CA1181514A - Semiconductor laser and method of making same - Google Patents
Semiconductor laser and method of making sameInfo
- Publication number
- CA1181514A CA1181514A CA000410176A CA410176A CA1181514A CA 1181514 A CA1181514 A CA 1181514A CA 000410176 A CA000410176 A CA 000410176A CA 410176 A CA410176 A CA 410176A CA 1181514 A CA1181514 A CA 1181514A
- Authority
- CA
- Canada
- Prior art keywords
- end zones
- active
- grooves
- mirror faces
- layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/16—Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface
- H01S5/162—Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface with window regions made by diffusion or disordening of the active layer
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/2054—Methods of obtaining the confinement
- H01S5/2059—Methods of obtaining the confinement by means of particular conductivity zones, e.g. obtained by particle bombardment or diffusion
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/2202—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure by making a groove in the upper laser structure
Abstract
ABSTRACT:
A semiconductor laser having mirror faces serving as resonators, in which the active laser region comprises end zones adjoining the mirror faces and com-prise implanted ions, preferably protons, with associated crystal damage. The end zones have a length which is at least equal to the diffusion length of the recombining charge carriers in the end zones. As a result of the high recombination rate in the end zones substantially no non-radiating recombination occurs at the mirror faces so that mirror erosion is avoided.
The invention also relates to a method in which the end zones are formed by an ion bombardment on the upper sur-face of the semiconductor wafer with a number of lasers, which wafer at the area of the mirror (oleavage) faces to be formed is provided with grooves which do not extend up to the active layer, in which grooves the end zones are provided via an ion bombardment through the active layer.
A semiconductor laser having mirror faces serving as resonators, in which the active laser region comprises end zones adjoining the mirror faces and com-prise implanted ions, preferably protons, with associated crystal damage. The end zones have a length which is at least equal to the diffusion length of the recombining charge carriers in the end zones. As a result of the high recombination rate in the end zones substantially no non-radiating recombination occurs at the mirror faces so that mirror erosion is avoided.
The invention also relates to a method in which the end zones are formed by an ion bombardment on the upper sur-face of the semiconductor wafer with a number of lasers, which wafer at the area of the mirror (oleavage) faces to be formed is provided with grooves which do not extend up to the active layer, in which grooves the end zones are provided via an ion bombardment through the active layer.
Description
~1~3~4 Pl~ 10 137 l 6-4 198 "Semiconductor laser and method of making same'~
The invention relates to a semiconductor laser having a semiconductor body co~prising an active laser region having a p-n junction, in which the active region is ~resent within a resonator which is formed by two mutually parallel reflecting non-oxidized mirror faces, in which contact members are present to apply current in the forward direction to the p-n junction~to generate coherent electromagnetic radiation in the active region, and in which the active region comprises end zones ad-joining the mirror faces so as to reduce non-radiating recombination near the mirror faces.
The invention relates in addition to a method of manufacturing the said semiconductor laser.
A semiconductor laser of the kind described is l~no~n from the article by Yonezu et al. in Applied Physics Letters 34 (1979) ~. 637~639.
In conventional semiconductor lasers in which the active region is present between reflecting surfaces of the crystal, also termed mirror faces, said mirror faces 20 tend to erode in the long run under the influence of non-radiating recombination at or near the mirror faces.
This tendency is particularly strong when the laser is operated in an atmosphere comprising water vapour, even when this is present only in a very small concentration 25 (for example9 1 : 105j. This mirror erosion gi~es rise to a gradual degradation of the properties of the laser~
inter alia to a continuous increase of the -threshold current and to the occurrence of pulsations in the emitted radi-ation. See, for example, J.A.Fo Peek in Electronics Letters 30 Vol. 16 No. 11, May 22, 1980, pp. 441-442, H.Yonezu et al.
in Journal of Applied Physics, 50(8), Au~ust, 19799 pP.
5150-5157, and F.R~Nash et al. in Applied Physics Letters, 35(12) December 15, 1979, pp~ 905-907. The cause of all this , ,.,~
5~
p~ 10 137 2 ~-4-1982 is that the reflecting proper-ties of the mirror faces rapidly cleteriorate as a resul-t of an increase of the roughness of -the said mirror races.
Said erosion can be mitigated in various manners.
For example, the water vapour can be elimina-ted, for example, by operating the laser in a vacuum. However, this necessitates a complicated an expensive encapsulation.
The rnirror faces may also be covered with a transparent dielectric protective layer. However, it is -technoligi-cally not simple to provide a readily adhering protectinglayer which is impervious to wa-ter vapour and has the correct thickness. A readily adhering and impervious pro-tecti~g layer can be ob-tained inter lia by -thermal oxi-dation of the mirror faces. However, this presents great problems in connection with the required high temperatures.
Since -the oxidation would have to be carried out after the metallisation of the laser so tha-t the oxide does not have to be removed for providing electrode layers, the oxidation temperature is restricted to that which the metallisation can stand. Undesired impurities from the metallisation may also enter the laser and the oxide.
Furthermore, undesired diffusion within the laser structure may take place. The use of oxidized mirror -faces is there-fore to be dissuaded.
From the publication JP-A53~61985 a method is known in which an improved thermal oxidation of the mirror faces is achieved by bombarding the mirror faces, prior to the oxidation, with ions, for example protons, so as to form an implanted layer having a -thickness smaller than the internal laser wavelength. The above-mentioned dis-advantages associated with thermal oxidation of the mirror faces are not obviated by this method.
It is also possible -to provide dielectric protecting layers by sputtering or vapour deposition.
However, in this manner also an efficacious protection of the mirror faces is technologically not easy to realise.
P~N lO 137 2a 7-4-1982 ~ rom the publication JP-A55-18078 a method is known in which on etched mesa mirror faces a dielectric layer is grown wllich is then bombarded wi-th protons so as to irnprove the resistance against erosion . fIowever, this method requires a-t least an extra etching step and the growth of a dielectric protective layer.
Another solution can be found by providing the acti-ve region with end zones which adjoin the mirror ~aces an~ have larger forbidden band gaps in which sub-stan-tially no radiation absorp-tion and consequently little non-radiating recombina-tion occwrs, as described in the above-menti~ned article by Yonezu e-t al.~in Applied Physics Letters 34 (1979) pp. 637-639. The selective zinc diffusion rnentioned in -this article, however, is complicated and not fully effective eit~r.
One of the objects of the invention is to PHN 10 137 3 6-~-1982 provide a laser structure in which the effect of non-radiating recombination near the mirror faces is con-siderably reduced by using end zones of a new structure which are more effective and which can be formed in a simple and reproducible manner. Another object of the invention is to provide a method in which the end zones of a large number of semiconductor lasers can be formed simultaneously before removing the lasers from the common semiconductor wafer in which they are manufacturedO
The invention is based inter alia on the re-cognition of the fact that these objec-ts may be achieved by using end zones having a high recombination rate so that the non-radiating recombination no longer occurs in the immediate proximity of but at some distance from 15 the mirror faces.
According to the invention a semiconductor laser of the kind described in the opening paragraph is characterized in that the end zones are formed by parts of the active region which comprise implanted 20 ions with associated crystal damage and extend from the mirror faces up to a distance which is at least equal to the diffusion length of recombining charge carriers in the end zones.
In the semiconductor laser structure according 25 to the invention non-radiating recombina-tion at the mirror faces is avoided because said recombination, as a result of the high recombination rate in the implanted end zones, takes place substantially entirely in par-ts of the end zones which are situated remote from the 30 mirror faces. As a result of this, erosion of the mirror faces is avoided or at least is reduced considerably.
~urthermore, providing end zones according to the inven-tion involves fewer technological problems than the al-ready mentioned diffusion techniques or -the provision 35 of protecting layers on the reflecting surfaces.
The implanted ions are prefera~ly protons which, due to their small mass, reach the desired penetration depth with comparatively low energy. In certain circum-s~
stances, deuterons or singly ionized hydrogen molecules may also be implanted advantageously instead of pro-tons.
However, the invention is no-t res-tricted thereto since other ions with associated crystal damage might also be implanted, if desired, so as to obtain the desired effect.
If -the end zones are formed by a proton bombard-ment, they preferably extend further than O.5/um and less than 5/um from the mirror faces. It has been found that end zones having a larger length, for example of 10/um, lO may have a detrimental influence on the laser properties while end zones having too small a length may not suffi-ciently prevent recombination at the mirror faces. As already said, the minimum length of the end zones is approximately equal to the diffusion length of the recom-15 bining charge carriers in the end zones~
The invention may be applied to any semiconduc-tor laser having mirror faces in which non-radiating recombination can occur at or near said mirror faces.
However, the invention may with particular advantage be 20 used in semiconductor lasers having a layer structure in which the active region is strip-shaped and forms part of an active semiconductor layer extending parallel to a major surface of the semiconductor body, the p-n junction being parallel to said active layer. In lasers having 25 this construction the ion bombardmen-t which is required for the formation of the end zones may advantageously be combined with an ion bombardment, in particular a proton bombardment, which is used for defining the strip-shaped active region. According to a preferred embodiment said 30 strip-shaped active region in its direc-tion of width is bounded laterally by a part of an ion-implanted region which also forms the end zones. The strip-shaped active region, however, may also be bounded laterally in many other manners instead of by a pro-ton bombardmentO In this 35 connection, many possibilities are known from the tech-nical literature.
Semiconductor lasers in accordance with the invention can be formed very advantageously and efficiently by using a method in which in a semiconductor wafer having a layer struc-ture suitable for the forma$ion of semicon-ductor lasers and comprising a-t least an active semicon-ductor layer extending parallel to a major surface of the 5 wafer9 grooves which extend down to a smaller depth than the active layer are provided at the area where cleavage surfaces serving as mirror faces are to be provided, ions are implanted in the grooves, the implanted zones with associa-ted crystal damage extending through the active 10 layer 7 after which the semiconductor wafer is divided by breaking into separate lasers thus forming the cleavage surfaces substan-tially normal to~the active layer at the area of the grooves, so -that the active layer of each laser obtains implanted end zones adjoining the cleavage 15 surfaces.
By using this method a large number of lasers with bombarded end zones can be manufactured on one semi-conductor wafer before severing the individual lasers by breaking.
The invention will now be described in greater detail, by way of example, with reference to a few embodi-ments and the drawing, in which Fig. 1 is a plan view of a semiconductor laser according to the invention, Figs. 2 and 3 are diagrammatic cross-sectional views of the semiconductor laser shown in Fig. 1 taken on the lines II-II and III-III, Figs. 4 to 6, 8 and 9 are diagrammatic cross-sectional views, and Fig. 7 is a plan view of successive stages of a method of manufacturing the semiconduc-tor laser accor-ding to -the invention, and Figs. 10A, B and 11A, B are cross-sectional views of a semiconductor wafer during the manufacture of a num-35ber of semiconductor lasers according to the invention.
The Figures are diagrammatic and not drawn to scale in which in particular the dimensions in the direction of thickness are exaggerated in the cross-~8~
sectional views.
~ ig. 1 is a plan view of a semicond~lctor laser according to the invention of which Figs, 2 and ~ are cross-sectional views taken on the lines II-II and III~
5 respectively, of l~ig. 1. The semiconductor laser of this example is a laser o~ the double hetero junction type 7 although the invention also applies to ~=~ lasers having a different construction. The laser has a semiconductor body 1 with an active laser region 2 which in this lO example is strip-shaped and forms part of an active semi-conduc-tor layer 3 which extends parallel to a major sur-face of the semiconductor body and which is present be-tween passive layers L~ and ~ which have a larger f`orbidden band gap than the active layer 3. The active laser region 15 2 comprises a p-n junction 6 which in this example is formed between the layers 3 and 5. However, in certain circumstances this ~ junction may be formed between the layers 3 and 4 or even within the layer 3 instead of be-tween the layers 3 and 5.
The active region 2 is present within a reso-nator which is formed by two mutually parallel reflecting non-oxidized mirror faces, in this case the side facets 7 and 8 of the crystal. Furthermore contact members are present in the form of two conductive electrode layers 9 25 and 10 with which current in the forward direction can be applied to the p-n junction 6 so as to generate coherent electromagnetic radiation in the active region 2 when the current rises above a given threshold value.
The active region 2 further comprises end zones 30 11, shaded in thè drawing, which adjoin the mirror faces 7 and 8. These end zones 11 serve to reduce non-radiating recombinations in the immediate proximity of the mirror faces 7 and 8 in a manner to be described in detail here-inafter. As a result of such non-radiating recombinations, 35 de~radation of the reflecting properties of the mirror faces 7 and 8 may in fact occur, According to the invention the end zones 11 are formed by parts of the active region 2 which comprise P~IN 10 137 7 6-4-1982 implanted ions with associated crystal clamage, which parts extend ~rom the mirror faces 7 and 8 up to a distance which is at least equal to the di~fusion length of re-combining charge carriers in the end zones. In this 5 example -the e~d zones comprise implanted protons and they extend up to approximately 1/um from the mirror faces 7 and 8. This is more than the diffusion length of holes and electrons in the zones 11 which diffusion length is only a few tenths of a /um As a result of the high recombination rate in the end zones 11 the recombination of electron-hole pairs generated in said zones by the laser radiation takes place nearly immediately on entering the zones 11, an~ at some distance before the mirror faces 7 and 8. Consequen-tly, l5 at the area of said mirror faces substantially no recom-bination takes place, the mirror faces 7 and 8 conserve their good reflecting properties much longer than in known lasers. As a result of this the lifetime of the semi-conductor laser according to the invention is considerably 20 increased.
The end zones 11 can be formed very accura-tely and reproducibly both as regards their dimensions and as regards their recombination rate because the ion implan-tation used is a readily controllable process which can 25 be controlled accurately via implantation energy, dose and possible "anneal" parameters.
The semiconductor laser according to the in-vention can be manufactured, for example, by carrying out, approximately normal to the mirror faces of the 30 finished laser structure (usually under a small deviation, in (110) mirror faces for example 7, relative to the perpendicular direction to prevent "channeling") a bom-bardment with ions which cause crystal damage down to the desired depth. This is carried out preferably by 35 means of a proton bombardment, although deuterons ~D~) or ionized hydrogen molecules (H2~) may also be used satisfactorily. When the ion bombardment takes place appro-ximately at right angles to the mirror surfaces, it will often be desirable to perform the bombardment with dif-ferent energies. This is to ensure that -the crystal damage which yields the required high recombina-tion rate is present over the whole length of the end zones. For example, in the embodiment described two proton bombardments, for example at 100 keV and at 50 keV, may be used each with a dose of 2 x 105 protons per cm .
The semiconductor laser shown in Figs. 1 to 3 may be constructed, for example, from a substrate 12 of lO N type GaAs having a thickness of 100/um, a doping of Si~atoms per cm3 and a surface having a (100) crystal orientation. Provided thereon are successively a flrst passive layer 4 (N type, composition Alo Ll~aO 6As, doping 5 x 10 tin atoms per cm , thickness 2/um), an active 15 layer 3 (undoped, composition Alo 0g~aO 91As, weak N
type, -thickness 0.2/um), a second passive layer 5 (P-type, composi-tion Alo 4GaO 6As, thickness 2/um, doping 5 x 1017 germanium atoms per cm3), and a contact layer 13 (P-type GaAs, doping 1018 germanium atoms per cm3, thickness 20 1/um). In this contact layer 13 finally, a P~ zinc dif-fusion 1~ is often provided down to a depth of approxi-mately 0.5/um so as to obtain a satisfac-tory low-ohmic contact. The laser thus constructed may emit a radiation beam having a wavelength of approximately 820 nm.
~5 The lateral boundary of the strip-shaped ac-tive region 2 was obtained in this case by a proton bombard-ment approximately at right angles to the major surface, in which the active region was masked9 for example, by a tungsten wire. As a result of -this the semiconductor layers 30 5 and 13 on either side of the active region 2 were made high-ohmic down to a depth of approximately 1.5/um, that is, dow to approximately 1.5/um of the active layer 3.
The high-ohmic zones 15 thus obtained are shown in Figs.
1 and 3.
Instead of by an ion bombardment transverse to the mirror faces it is also possible to provide the end zones 11 prior to the formation of the mirror faces, while the lasers still form part of the semiconductor PHN 10 137 9 6-~-1982 wafer on which they are ~ormed. The ion bombardment is carried out approximately at right angles to the semi-conductor wafer and by means of a suitable masking and by controlling the implantation energy it is controlled 5 so that at the area o~ the end zones to be formed the crystal damage extends through the active layer 3 and, in the regions on either side o~ the strip-shaped active regions 2, remains remote from the layer 3 prererably by approximately 1.5/um. The semiconductor wafer is then lO severed into individual lasers in such manner that cleavage sur~aces are formed which serve as mirror faces and bound the bombarded end zones. In -that case no double bornbardment at different energies is necessary -to make the crystal damage in the end zones 11 homogeneous~ since l5 the layer 3 has only a very small thickness. The ~act -that the dimension of t~e end zones 11 in a direction normal to the mirror faces is only a few /um, however, makes it dif~icult to provide the cleavage sur~aces ser-ving as mirror faces in the correct place.
A method in which this can nevertheless be done in a comparatively simple manner will now be illustrated with reference to Figs. 4 to 9.
The starting material is a semiconductor wafer having a layer structure suitable for the formation of semi-25 conductor lasers. As an example the same layer structure is used here as in the example according to Figs. 1 to 3 but other layer structures may of course be used instead thereof. In this layer structure consisting (see Fig. 4) of the substrate 12, the passive layers 4 and 5, the ac-30 tive layer 3 and the contact layer 13, grooves 20 areprovided be~ore carrying out a zinc diffusion 14~ at -the area of the cleavage surfaces serving as mirror faces to be p~ovided~ ~hich grooves extend down -to a smaller depth than the active layer 3. In this example, mutually parallel 35 V-shaped grooves 20 are etched at distances of approxi-mately 250/um ~rom each other which extend in the (110)-direction on the (100) oriented surface of the semicon-ductor wafer and the walls of which are formed substan-PIIN 10 137 10 6-4-l982 tially by (111) ~aces. These grooves have a depth of approximately 1.5/um. Since the thickness of the layer 13 is appro~imately l/um and that of the layer 5 is approxi-ma-tely 2/um, the deepest point of the grooves 11 is at 5 approximately 1.5/um from the active layer 3. The grooves may be provided by means of a preferential e-tching process in which, for example, a radiation-sensitive lacquer layer (photolacquer layer), electron resist or the like is used as a masking and, for example 9 a preferential e-tching 10 liquid which contains NH~O~I, H202 and water is used as an etchant. Herewith ~-shaped grooves having walls which ~orm approximately (111) faces and make a~ angle o~
approximately 54 with the ~100) face are formed in a (110) plane. This way of etching makes it possible to accurately l5 control the depth of the grooves. Di~ferently shaped grooves and other etching methods, for example plasma etching, may also be used provided the semiconductor wafer can be cleaved -thereby in the direction of the groo-ves according to planes which are at right angles to 20 the major surface.
A~ter etching and after removing the ctching mask, zinc is diffused in the upper surface and in the groove walls, so as to obtain a good ohmic contact, ~or example, down to a depth of approximately 0.5/um so that 25 a P~ layer 14 is formed in the contact layer 13. In cer-tain circumstances this zinc diffusion may be omitted, for example, when alloyed electrodes are used.
In the Fig. 4 structure obtained in this manner a 50 nm thick chromium layer and thereon a 100 nm thick 30 platinum layer are successively sputtered on the upper surface and in the grooves. The g~ooves 20 are -then ~illed with a photolacquer 21. This may be done, for example, by providing (positive) photosensitive lacquer over the while surface and exposing said photolacquer ~rom above 35 down to such a depth that upon developing the photolacquer remains only in the grooves. A l/um thick gold layer 23 is then deposited electrolytically on the upper surface outside the grooves 20, see Fig. 5. The photolacquer 21 PHN 10 137 11 6~4-1982 is then removed from the grooves 20~ for example by plasma etching, after which (see Fig. 6) protons are implanted in -the major surface in the direction of the arrows, thus ~orming implanted zones 11 (shaded in Fig. 6~ wit~ asso-ciated crystal damage which in any case extend partlythrough the active layer 3. In this proton implantation the gold layer 23 in combination with the underlying thinner chromium-platinum layer 22 serves as a mask.
After removing the gold layer 23 the strip-shaped lO active regions of the lasers are defined by a second proton bombardment to form high-ohmic r~ones 15 extending down -to approximately 1~5/um from the active layer in ac-cordance with Fig. 7 which is a plan view of a part of the semiconductor wafer in this stage. As a masking in this 15 latter proton bombardment is used as a rule a grating of me-tal wires, ~or example tungsten wires, present on or directly above the surface.
Finally, after providing the substrate on the lower side with an electrode layer, for example a gold-20 germanium layer 10, the semiconductor wafer is severed intoindividual lasers by scribing and breaking, in which cleavage surfaces 16 (see Fig. 7) serving as mirror sur-faces 7 and 8 are ob~ained according to the grooves 20.
Cleaving can simply be carried out by providing a diamond 25 scribe in the end of the groove.
The individual lasers obtained in this manner have a cross-section which is shown diagrammatically in Fig. 8 in the longitudinal direction and in Fig. g in -the direc-tion of width. Characteristic is tha-t the side faces 30 Of the crystal which form the mirror ~aces 7 and 8 out-side the active region show facets which are formed by the walls of -the originally provided V-grooves~ It is to be noted that in the last-described example the zinc dif~usion may also be carried out prior to etching the 35 grooves. In order -to avoid problems in the subsequent etching with a difference in etching rate between the dif-fused and the non-diffused con-tact layer parts 9 first the di~used layer 14 may be removed at the area of the grooves PHN 10 137 12 ~-4-1982 to be etched, for example 9 by means of an isotopic etching liquid or by means of plasma etching, af`ter which the V-grooves are formed by means of a preferential etchant.
According to an important modified embodiment the implantations to form the zones 11 and 15 can be carried out by means of the same masking without removing the semiconductor wafer from the apparatus. For that pur-pose, a masking in the form of ~ires 30, for example, tungsten wires~ extending transversely across the grooves, lO is provided after providing the grooves 20 at the area of the strip-shaped active regions 2 to be formed. See Figs~
10~, B in a cross-sectional view along a groove and Figs.
11~, B in a`cross-section at righ-t angles to the grooves.
The ion implantation, in this example a proton bombardment, 15 is then carried out in the form of successive (in this example i-wo) implantations at different angles (~ ) wi-th the major surface 31. The angles ~ and ~ are chosen such that the implanted regions overlap each other on and near the bottom 32 of the grooves 20 (see Fig. 10B) thus 20 forming the zone 11 which penetrates through the active ~ayer, but on and near the major surface 31 on either side of the wires 30 ~orm zones 15 which are mutually separated.
For reasons of clarity, the layers 3, 4 and 5 are not sho~n in Figso 10A, B and 11A, B.
Although only lasers of the double hetero junc-tion type of the most usual structure were described in the example, the invention is by no means restricted thereto.
For example, the invention is also advantageous in lasers in ~hich the ~_ junction is not parallel but a-t right 30 angles to the active layer, for example, in laser struc-tures of the so-called TJS (Transverse Junction Stripe) type described inter alia in United States Patent Specifi-cation 3,961,9~6. In general, the invention may advantage-ously be used in any semiconduc-tor laser in which non-35 radiating recombination near the mirror faces may occurand should be avoided. An important advantage of -the invention is that the bombarded mirror faces need not necessarily be provided ~.8~
with a dielectric protective layer, although a vapour-deposited dielectric protective layer can produce an even further improvement of the lifetime of the laser.
Instead of the semiconductor materials described 5 in the examples, of course other semiconductor materials suitable for the manufacture o~ p-n semiconductor lasers may be used. Within the scope of -the invention other electrode structures and electrode materials may also be used, while the conductivity types given in the examples lO may also be replaced (simultaneously) by their opposite ones.
~ comparison of otherwise identical semiconduc-tor laser structures demonstrated that in non-bombarded mirror faces degradation and pulsations occurred after a few 15 hours already, while in bombarded mirror faces according to the invention no degrada-tion was observable after 350 hours continuous (c~) operation at 10 mW power.
The invention relates to a semiconductor laser having a semiconductor body co~prising an active laser region having a p-n junction, in which the active region is ~resent within a resonator which is formed by two mutually parallel reflecting non-oxidized mirror faces, in which contact members are present to apply current in the forward direction to the p-n junction~to generate coherent electromagnetic radiation in the active region, and in which the active region comprises end zones ad-joining the mirror faces so as to reduce non-radiating recombination near the mirror faces.
The invention relates in addition to a method of manufacturing the said semiconductor laser.
A semiconductor laser of the kind described is l~no~n from the article by Yonezu et al. in Applied Physics Letters 34 (1979) ~. 637~639.
In conventional semiconductor lasers in which the active region is present between reflecting surfaces of the crystal, also termed mirror faces, said mirror faces 20 tend to erode in the long run under the influence of non-radiating recombination at or near the mirror faces.
This tendency is particularly strong when the laser is operated in an atmosphere comprising water vapour, even when this is present only in a very small concentration 25 (for example9 1 : 105j. This mirror erosion gi~es rise to a gradual degradation of the properties of the laser~
inter alia to a continuous increase of the -threshold current and to the occurrence of pulsations in the emitted radi-ation. See, for example, J.A.Fo Peek in Electronics Letters 30 Vol. 16 No. 11, May 22, 1980, pp. 441-442, H.Yonezu et al.
in Journal of Applied Physics, 50(8), Au~ust, 19799 pP.
5150-5157, and F.R~Nash et al. in Applied Physics Letters, 35(12) December 15, 1979, pp~ 905-907. The cause of all this , ,.,~
5~
p~ 10 137 2 ~-4-1982 is that the reflecting proper-ties of the mirror faces rapidly cleteriorate as a resul-t of an increase of the roughness of -the said mirror races.
Said erosion can be mitigated in various manners.
For example, the water vapour can be elimina-ted, for example, by operating the laser in a vacuum. However, this necessitates a complicated an expensive encapsulation.
The rnirror faces may also be covered with a transparent dielectric protective layer. However, it is -technoligi-cally not simple to provide a readily adhering protectinglayer which is impervious to wa-ter vapour and has the correct thickness. A readily adhering and impervious pro-tecti~g layer can be ob-tained inter lia by -thermal oxi-dation of the mirror faces. However, this presents great problems in connection with the required high temperatures.
Since -the oxidation would have to be carried out after the metallisation of the laser so tha-t the oxide does not have to be removed for providing electrode layers, the oxidation temperature is restricted to that which the metallisation can stand. Undesired impurities from the metallisation may also enter the laser and the oxide.
Furthermore, undesired diffusion within the laser structure may take place. The use of oxidized mirror -faces is there-fore to be dissuaded.
From the publication JP-A53~61985 a method is known in which an improved thermal oxidation of the mirror faces is achieved by bombarding the mirror faces, prior to the oxidation, with ions, for example protons, so as to form an implanted layer having a -thickness smaller than the internal laser wavelength. The above-mentioned dis-advantages associated with thermal oxidation of the mirror faces are not obviated by this method.
It is also possible -to provide dielectric protecting layers by sputtering or vapour deposition.
However, in this manner also an efficacious protection of the mirror faces is technologically not easy to realise.
P~N lO 137 2a 7-4-1982 ~ rom the publication JP-A55-18078 a method is known in which on etched mesa mirror faces a dielectric layer is grown wllich is then bombarded wi-th protons so as to irnprove the resistance against erosion . fIowever, this method requires a-t least an extra etching step and the growth of a dielectric protective layer.
Another solution can be found by providing the acti-ve region with end zones which adjoin the mirror ~aces an~ have larger forbidden band gaps in which sub-stan-tially no radiation absorp-tion and consequently little non-radiating recombina-tion occwrs, as described in the above-menti~ned article by Yonezu e-t al.~in Applied Physics Letters 34 (1979) pp. 637-639. The selective zinc diffusion rnentioned in -this article, however, is complicated and not fully effective eit~r.
One of the objects of the invention is to PHN 10 137 3 6-~-1982 provide a laser structure in which the effect of non-radiating recombination near the mirror faces is con-siderably reduced by using end zones of a new structure which are more effective and which can be formed in a simple and reproducible manner. Another object of the invention is to provide a method in which the end zones of a large number of semiconductor lasers can be formed simultaneously before removing the lasers from the common semiconductor wafer in which they are manufacturedO
The invention is based inter alia on the re-cognition of the fact that these objec-ts may be achieved by using end zones having a high recombination rate so that the non-radiating recombination no longer occurs in the immediate proximity of but at some distance from 15 the mirror faces.
According to the invention a semiconductor laser of the kind described in the opening paragraph is characterized in that the end zones are formed by parts of the active region which comprise implanted 20 ions with associated crystal damage and extend from the mirror faces up to a distance which is at least equal to the diffusion length of recombining charge carriers in the end zones.
In the semiconductor laser structure according 25 to the invention non-radiating recombina-tion at the mirror faces is avoided because said recombination, as a result of the high recombination rate in the implanted end zones, takes place substantially entirely in par-ts of the end zones which are situated remote from the 30 mirror faces. As a result of this, erosion of the mirror faces is avoided or at least is reduced considerably.
~urthermore, providing end zones according to the inven-tion involves fewer technological problems than the al-ready mentioned diffusion techniques or -the provision 35 of protecting layers on the reflecting surfaces.
The implanted ions are prefera~ly protons which, due to their small mass, reach the desired penetration depth with comparatively low energy. In certain circum-s~
stances, deuterons or singly ionized hydrogen molecules may also be implanted advantageously instead of pro-tons.
However, the invention is no-t res-tricted thereto since other ions with associated crystal damage might also be implanted, if desired, so as to obtain the desired effect.
If -the end zones are formed by a proton bombard-ment, they preferably extend further than O.5/um and less than 5/um from the mirror faces. It has been found that end zones having a larger length, for example of 10/um, lO may have a detrimental influence on the laser properties while end zones having too small a length may not suffi-ciently prevent recombination at the mirror faces. As already said, the minimum length of the end zones is approximately equal to the diffusion length of the recom-15 bining charge carriers in the end zones~
The invention may be applied to any semiconduc-tor laser having mirror faces in which non-radiating recombination can occur at or near said mirror faces.
However, the invention may with particular advantage be 20 used in semiconductor lasers having a layer structure in which the active region is strip-shaped and forms part of an active semiconductor layer extending parallel to a major surface of the semiconductor body, the p-n junction being parallel to said active layer. In lasers having 25 this construction the ion bombardmen-t which is required for the formation of the end zones may advantageously be combined with an ion bombardment, in particular a proton bombardment, which is used for defining the strip-shaped active region. According to a preferred embodiment said 30 strip-shaped active region in its direc-tion of width is bounded laterally by a part of an ion-implanted region which also forms the end zones. The strip-shaped active region, however, may also be bounded laterally in many other manners instead of by a pro-ton bombardmentO In this 35 connection, many possibilities are known from the tech-nical literature.
Semiconductor lasers in accordance with the invention can be formed very advantageously and efficiently by using a method in which in a semiconductor wafer having a layer struc-ture suitable for the forma$ion of semicon-ductor lasers and comprising a-t least an active semicon-ductor layer extending parallel to a major surface of the 5 wafer9 grooves which extend down to a smaller depth than the active layer are provided at the area where cleavage surfaces serving as mirror faces are to be provided, ions are implanted in the grooves, the implanted zones with associa-ted crystal damage extending through the active 10 layer 7 after which the semiconductor wafer is divided by breaking into separate lasers thus forming the cleavage surfaces substan-tially normal to~the active layer at the area of the grooves, so -that the active layer of each laser obtains implanted end zones adjoining the cleavage 15 surfaces.
By using this method a large number of lasers with bombarded end zones can be manufactured on one semi-conductor wafer before severing the individual lasers by breaking.
The invention will now be described in greater detail, by way of example, with reference to a few embodi-ments and the drawing, in which Fig. 1 is a plan view of a semiconductor laser according to the invention, Figs. 2 and 3 are diagrammatic cross-sectional views of the semiconductor laser shown in Fig. 1 taken on the lines II-II and III-III, Figs. 4 to 6, 8 and 9 are diagrammatic cross-sectional views, and Fig. 7 is a plan view of successive stages of a method of manufacturing the semiconduc-tor laser accor-ding to -the invention, and Figs. 10A, B and 11A, B are cross-sectional views of a semiconductor wafer during the manufacture of a num-35ber of semiconductor lasers according to the invention.
The Figures are diagrammatic and not drawn to scale in which in particular the dimensions in the direction of thickness are exaggerated in the cross-~8~
sectional views.
~ ig. 1 is a plan view of a semicond~lctor laser according to the invention of which Figs, 2 and ~ are cross-sectional views taken on the lines II-II and III~
5 respectively, of l~ig. 1. The semiconductor laser of this example is a laser o~ the double hetero junction type 7 although the invention also applies to ~=~ lasers having a different construction. The laser has a semiconductor body 1 with an active laser region 2 which in this lO example is strip-shaped and forms part of an active semi-conduc-tor layer 3 which extends parallel to a major sur-face of the semiconductor body and which is present be-tween passive layers L~ and ~ which have a larger f`orbidden band gap than the active layer 3. The active laser region 15 2 comprises a p-n junction 6 which in this example is formed between the layers 3 and 5. However, in certain circumstances this ~ junction may be formed between the layers 3 and 4 or even within the layer 3 instead of be-tween the layers 3 and 5.
The active region 2 is present within a reso-nator which is formed by two mutually parallel reflecting non-oxidized mirror faces, in this case the side facets 7 and 8 of the crystal. Furthermore contact members are present in the form of two conductive electrode layers 9 25 and 10 with which current in the forward direction can be applied to the p-n junction 6 so as to generate coherent electromagnetic radiation in the active region 2 when the current rises above a given threshold value.
The active region 2 further comprises end zones 30 11, shaded in thè drawing, which adjoin the mirror faces 7 and 8. These end zones 11 serve to reduce non-radiating recombinations in the immediate proximity of the mirror faces 7 and 8 in a manner to be described in detail here-inafter. As a result of such non-radiating recombinations, 35 de~radation of the reflecting properties of the mirror faces 7 and 8 may in fact occur, According to the invention the end zones 11 are formed by parts of the active region 2 which comprise P~IN 10 137 7 6-4-1982 implanted ions with associated crystal clamage, which parts extend ~rom the mirror faces 7 and 8 up to a distance which is at least equal to the di~fusion length of re-combining charge carriers in the end zones. In this 5 example -the e~d zones comprise implanted protons and they extend up to approximately 1/um from the mirror faces 7 and 8. This is more than the diffusion length of holes and electrons in the zones 11 which diffusion length is only a few tenths of a /um As a result of the high recombination rate in the end zones 11 the recombination of electron-hole pairs generated in said zones by the laser radiation takes place nearly immediately on entering the zones 11, an~ at some distance before the mirror faces 7 and 8. Consequen-tly, l5 at the area of said mirror faces substantially no recom-bination takes place, the mirror faces 7 and 8 conserve their good reflecting properties much longer than in known lasers. As a result of this the lifetime of the semi-conductor laser according to the invention is considerably 20 increased.
The end zones 11 can be formed very accura-tely and reproducibly both as regards their dimensions and as regards their recombination rate because the ion implan-tation used is a readily controllable process which can 25 be controlled accurately via implantation energy, dose and possible "anneal" parameters.
The semiconductor laser according to the in-vention can be manufactured, for example, by carrying out, approximately normal to the mirror faces of the 30 finished laser structure (usually under a small deviation, in (110) mirror faces for example 7, relative to the perpendicular direction to prevent "channeling") a bom-bardment with ions which cause crystal damage down to the desired depth. This is carried out preferably by 35 means of a proton bombardment, although deuterons ~D~) or ionized hydrogen molecules (H2~) may also be used satisfactorily. When the ion bombardment takes place appro-ximately at right angles to the mirror surfaces, it will often be desirable to perform the bombardment with dif-ferent energies. This is to ensure that -the crystal damage which yields the required high recombina-tion rate is present over the whole length of the end zones. For example, in the embodiment described two proton bombardments, for example at 100 keV and at 50 keV, may be used each with a dose of 2 x 105 protons per cm .
The semiconductor laser shown in Figs. 1 to 3 may be constructed, for example, from a substrate 12 of lO N type GaAs having a thickness of 100/um, a doping of Si~atoms per cm3 and a surface having a (100) crystal orientation. Provided thereon are successively a flrst passive layer 4 (N type, composition Alo Ll~aO 6As, doping 5 x 10 tin atoms per cm , thickness 2/um), an active 15 layer 3 (undoped, composition Alo 0g~aO 91As, weak N
type, -thickness 0.2/um), a second passive layer 5 (P-type, composi-tion Alo 4GaO 6As, thickness 2/um, doping 5 x 1017 germanium atoms per cm3), and a contact layer 13 (P-type GaAs, doping 1018 germanium atoms per cm3, thickness 20 1/um). In this contact layer 13 finally, a P~ zinc dif-fusion 1~ is often provided down to a depth of approxi-mately 0.5/um so as to obtain a satisfac-tory low-ohmic contact. The laser thus constructed may emit a radiation beam having a wavelength of approximately 820 nm.
~5 The lateral boundary of the strip-shaped ac-tive region 2 was obtained in this case by a proton bombard-ment approximately at right angles to the major surface, in which the active region was masked9 for example, by a tungsten wire. As a result of -this the semiconductor layers 30 5 and 13 on either side of the active region 2 were made high-ohmic down to a depth of approximately 1.5/um, that is, dow to approximately 1.5/um of the active layer 3.
The high-ohmic zones 15 thus obtained are shown in Figs.
1 and 3.
Instead of by an ion bombardment transverse to the mirror faces it is also possible to provide the end zones 11 prior to the formation of the mirror faces, while the lasers still form part of the semiconductor PHN 10 137 9 6-~-1982 wafer on which they are ~ormed. The ion bombardment is carried out approximately at right angles to the semi-conductor wafer and by means of a suitable masking and by controlling the implantation energy it is controlled 5 so that at the area o~ the end zones to be formed the crystal damage extends through the active layer 3 and, in the regions on either side o~ the strip-shaped active regions 2, remains remote from the layer 3 prererably by approximately 1.5/um. The semiconductor wafer is then lO severed into individual lasers in such manner that cleavage sur~aces are formed which serve as mirror faces and bound the bombarded end zones. In -that case no double bornbardment at different energies is necessary -to make the crystal damage in the end zones 11 homogeneous~ since l5 the layer 3 has only a very small thickness. The ~act -that the dimension of t~e end zones 11 in a direction normal to the mirror faces is only a few /um, however, makes it dif~icult to provide the cleavage sur~aces ser-ving as mirror faces in the correct place.
A method in which this can nevertheless be done in a comparatively simple manner will now be illustrated with reference to Figs. 4 to 9.
The starting material is a semiconductor wafer having a layer structure suitable for the formation of semi-25 conductor lasers. As an example the same layer structure is used here as in the example according to Figs. 1 to 3 but other layer structures may of course be used instead thereof. In this layer structure consisting (see Fig. 4) of the substrate 12, the passive layers 4 and 5, the ac-30 tive layer 3 and the contact layer 13, grooves 20 areprovided be~ore carrying out a zinc diffusion 14~ at -the area of the cleavage surfaces serving as mirror faces to be p~ovided~ ~hich grooves extend down -to a smaller depth than the active layer 3. In this example, mutually parallel 35 V-shaped grooves 20 are etched at distances of approxi-mately 250/um ~rom each other which extend in the (110)-direction on the (100) oriented surface of the semicon-ductor wafer and the walls of which are formed substan-PIIN 10 137 10 6-4-l982 tially by (111) ~aces. These grooves have a depth of approximately 1.5/um. Since the thickness of the layer 13 is appro~imately l/um and that of the layer 5 is approxi-ma-tely 2/um, the deepest point of the grooves 11 is at 5 approximately 1.5/um from the active layer 3. The grooves may be provided by means of a preferential e-tching process in which, for example, a radiation-sensitive lacquer layer (photolacquer layer), electron resist or the like is used as a masking and, for example 9 a preferential e-tching 10 liquid which contains NH~O~I, H202 and water is used as an etchant. Herewith ~-shaped grooves having walls which ~orm approximately (111) faces and make a~ angle o~
approximately 54 with the ~100) face are formed in a (110) plane. This way of etching makes it possible to accurately l5 control the depth of the grooves. Di~ferently shaped grooves and other etching methods, for example plasma etching, may also be used provided the semiconductor wafer can be cleaved -thereby in the direction of the groo-ves according to planes which are at right angles to 20 the major surface.
A~ter etching and after removing the ctching mask, zinc is diffused in the upper surface and in the groove walls, so as to obtain a good ohmic contact, ~or example, down to a depth of approximately 0.5/um so that 25 a P~ layer 14 is formed in the contact layer 13. In cer-tain circumstances this zinc diffusion may be omitted, for example, when alloyed electrodes are used.
In the Fig. 4 structure obtained in this manner a 50 nm thick chromium layer and thereon a 100 nm thick 30 platinum layer are successively sputtered on the upper surface and in the grooves. The g~ooves 20 are -then ~illed with a photolacquer 21. This may be done, for example, by providing (positive) photosensitive lacquer over the while surface and exposing said photolacquer ~rom above 35 down to such a depth that upon developing the photolacquer remains only in the grooves. A l/um thick gold layer 23 is then deposited electrolytically on the upper surface outside the grooves 20, see Fig. 5. The photolacquer 21 PHN 10 137 11 6~4-1982 is then removed from the grooves 20~ for example by plasma etching, after which (see Fig. 6) protons are implanted in -the major surface in the direction of the arrows, thus ~orming implanted zones 11 (shaded in Fig. 6~ wit~ asso-ciated crystal damage which in any case extend partlythrough the active layer 3. In this proton implantation the gold layer 23 in combination with the underlying thinner chromium-platinum layer 22 serves as a mask.
After removing the gold layer 23 the strip-shaped lO active regions of the lasers are defined by a second proton bombardment to form high-ohmic r~ones 15 extending down -to approximately 1~5/um from the active layer in ac-cordance with Fig. 7 which is a plan view of a part of the semiconductor wafer in this stage. As a masking in this 15 latter proton bombardment is used as a rule a grating of me-tal wires, ~or example tungsten wires, present on or directly above the surface.
Finally, after providing the substrate on the lower side with an electrode layer, for example a gold-20 germanium layer 10, the semiconductor wafer is severed intoindividual lasers by scribing and breaking, in which cleavage surfaces 16 (see Fig. 7) serving as mirror sur-faces 7 and 8 are ob~ained according to the grooves 20.
Cleaving can simply be carried out by providing a diamond 25 scribe in the end of the groove.
The individual lasers obtained in this manner have a cross-section which is shown diagrammatically in Fig. 8 in the longitudinal direction and in Fig. g in -the direc-tion of width. Characteristic is tha-t the side faces 30 Of the crystal which form the mirror ~aces 7 and 8 out-side the active region show facets which are formed by the walls of -the originally provided V-grooves~ It is to be noted that in the last-described example the zinc dif~usion may also be carried out prior to etching the 35 grooves. In order -to avoid problems in the subsequent etching with a difference in etching rate between the dif-fused and the non-diffused con-tact layer parts 9 first the di~used layer 14 may be removed at the area of the grooves PHN 10 137 12 ~-4-1982 to be etched, for example 9 by means of an isotopic etching liquid or by means of plasma etching, af`ter which the V-grooves are formed by means of a preferential etchant.
According to an important modified embodiment the implantations to form the zones 11 and 15 can be carried out by means of the same masking without removing the semiconductor wafer from the apparatus. For that pur-pose, a masking in the form of ~ires 30, for example, tungsten wires~ extending transversely across the grooves, lO is provided after providing the grooves 20 at the area of the strip-shaped active regions 2 to be formed. See Figs~
10~, B in a cross-sectional view along a groove and Figs.
11~, B in a`cross-section at righ-t angles to the grooves.
The ion implantation, in this example a proton bombardment, 15 is then carried out in the form of successive (in this example i-wo) implantations at different angles (~ ) wi-th the major surface 31. The angles ~ and ~ are chosen such that the implanted regions overlap each other on and near the bottom 32 of the grooves 20 (see Fig. 10B) thus 20 forming the zone 11 which penetrates through the active ~ayer, but on and near the major surface 31 on either side of the wires 30 ~orm zones 15 which are mutually separated.
For reasons of clarity, the layers 3, 4 and 5 are not sho~n in Figso 10A, B and 11A, B.
Although only lasers of the double hetero junc-tion type of the most usual structure were described in the example, the invention is by no means restricted thereto.
For example, the invention is also advantageous in lasers in ~hich the ~_ junction is not parallel but a-t right 30 angles to the active layer, for example, in laser struc-tures of the so-called TJS (Transverse Junction Stripe) type described inter alia in United States Patent Specifi-cation 3,961,9~6. In general, the invention may advantage-ously be used in any semiconduc-tor laser in which non-35 radiating recombination near the mirror faces may occurand should be avoided. An important advantage of -the invention is that the bombarded mirror faces need not necessarily be provided ~.8~
with a dielectric protective layer, although a vapour-deposited dielectric protective layer can produce an even further improvement of the lifetime of the laser.
Instead of the semiconductor materials described 5 in the examples, of course other semiconductor materials suitable for the manufacture o~ p-n semiconductor lasers may be used. Within the scope of -the invention other electrode structures and electrode materials may also be used, while the conductivity types given in the examples lO may also be replaced (simultaneously) by their opposite ones.
~ comparison of otherwise identical semiconduc-tor laser structures demonstrated that in non-bombarded mirror faces degradation and pulsations occurred after a few 15 hours already, while in bombarded mirror faces according to the invention no degrada-tion was observable after 350 hours continuous (c~) operation at 10 mW power.
Claims (10)
1. A semiconductor laser having a semiconductor body comprising an active laser region having a p-n junc-tion, in which the active region is present within a resonator which is formed by two mutually parallel reflec-ting non-oxidized mirror faces, in which contact members are present to supply current in the forward direction to the p-n junction to generate coherent electromagnetic radiation in the active region, and in which the active region comprises end zones adjoining the mirror faces to reduce non-radiating recombination near the mirror faces, characterized in that the end zones are formed by parts of the active region which comprise implanted ions with associated crystal damage and extend from the mirror faces up to a distance which is at least equal to the diffusion length of recombining charge carriers in the end zones.
2. A semiconductor laser as claimed in Claim 1, characterized in that the implanted ions are protons.
3. A semiconductor laser as claimed in Claim 1, characterized in that the implanted ions are deuterons (D+) or singly ionized hydrogen molecules (H2+).
4. A semiconductor laser as claimed in Claim 2, characterized in that the end zones extend from the mirror faces up to a distance which is larger than 0.5?/um and is smaller than 5?/um.
5. A semiconductor laser as claimed in Claim 1, characterized in that the laser is constructed from a latex structure in which the active region is strip-shaped and forms part of an active semiconductor layer extending parallel to a major surface of the semiconduc-tor body, the p-n junction extending parallel to said active layer.
6. A semiconductor laser as claimed in Claim 5, characterized in that the strip-shaped active region in its direction of width is bounded laterally by a part of an ion-implanted region which also forms the end zones.
7. A method of manufacturing a semiconductor laser as claimed in Claim 1, characterized in that in a semiconductor body having a layer structure suitable for the formation of semiconductor lasers and comprising at least an active semiconductor layer extending parallel to a major surface of the body, grooves extending down to a smaller depth than the active layer are provided at the area where cleavage surfaces serving as mirror faces are to be provided, that ions are implanted in the grooves, the implanted zones with associated crystal damage extending through the active layer, and that the semicon-ductor wafer is then divided by breaking into separate lasers, thus forming the cleavage surfaces substantially normal to the active layer at the area of the grooves, so that the active layer of each laser obtains implanted end zones adjoining the cleavage surfaces.
8. A method as claimed in Claim 7, characterized in that the grooves are V-shaped and are provided by using a preferential etching process.
9. A method as claimed in Claim 7, characterized in that the major surface has a (100) orientation, that the cleavage surfaces. are (110) crystal facets, and that the groove walls are formed substantially by (111) planes.
10. A method as claimed in Claim 7, characterized in that after providing the grooves at the area of the strip-shaped active regions to be formed there is provided a mask in the form of wires extending transversely across the grooves and that then the said ion implantation is carried out by successive implantations, said implantations being carried out at different angles with respect to the major surface said angles being chosen such that implanted regions overlap each other on and near the bottom of the groove but are separated from each other on and near the major surface on either side of the wires.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8104068A NL8104068A (en) | 1981-09-02 | 1981-09-02 | SEMICONDUCTOR LASER. |
| NL8104068 | 1981-09-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1181514A true CA1181514A (en) | 1985-01-22 |
Family
ID=19838001
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000410176A Expired CA1181514A (en) | 1981-09-02 | 1982-08-26 | Semiconductor laser and method of making same |
Country Status (6)
| Country | Link |
|---|---|
| US (2) | US4558448A (en) |
| EP (1) | EP0073548B1 (en) |
| JP (1) | JPS5852894A (en) |
| CA (1) | CA1181514A (en) |
| DE (1) | DE3263763D1 (en) |
| NL (1) | NL8104068A (en) |
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|---|---|---|---|---|
| FR2562339B1 (en) * | 1984-04-03 | 1986-06-20 | Bouadma Noureddine | METHOD FOR PRODUCING A SEMICONDUCTOR LASER MIRROR BY ION MACHINING |
| JPH0712099B2 (en) * | 1984-12-24 | 1995-02-08 | 株式会社日立製作所 | Method for manufacturing semiconductor laser device |
| JPS62130581A (en) * | 1985-11-30 | 1987-06-12 | Fujitsu Ltd | Semiconductor laser |
| JPS63124486A (en) * | 1986-11-13 | 1988-05-27 | Mitsubishi Electric Corp | Manufacture of semiconductor laser |
| JPH0614575B2 (en) * | 1987-07-10 | 1994-02-23 | シャープ株式会社 | Semiconductor laser device |
| JPH0671121B2 (en) * | 1987-09-04 | 1994-09-07 | シャープ株式会社 | Semiconductor laser device |
| DE3834929A1 (en) * | 1988-10-13 | 1990-04-19 | Siemens Ag | Optical waveguide reflector for optoelectronic applications and lasers |
| US5593815A (en) * | 1989-07-31 | 1997-01-14 | Goldstar Co., Ltd. | Cleaving process in manufacturing a semiconductor laser |
| JPH0635160U (en) * | 1992-10-14 | 1994-05-10 | 株式会社吉野工業所 | Seal material |
| US5463647A (en) * | 1993-02-25 | 1995-10-31 | The United States Of America As Represented By The Secretary Of The Air Force | Broadband multi-wavelength narrow linewidth laser source using an electro-optic modulator |
| JP3360105B2 (en) * | 1994-03-04 | 2002-12-24 | 富士通株式会社 | Method for manufacturing semiconductor device |
| KR0141057B1 (en) * | 1994-11-19 | 1998-07-15 | 이헌조 | A method of manufacturing semiconductor laser |
| JPH10223992A (en) * | 1997-01-31 | 1998-08-21 | Oki Electric Ind Co Ltd | Manufacture of semiconductor element |
| EP1866955A4 (en) * | 2005-03-25 | 2011-02-02 | Trumpf Photonics Inc | Laser facet passivation |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4994292A (en) * | 1973-01-11 | 1974-09-06 | ||
| US3838359A (en) * | 1973-11-23 | 1974-09-24 | Bell Telephone Labor Inc | Gain asymmetry in heterostructure junction lasers operating in a fundamental transverse mode |
| JPS516491A (en) * | 1974-07-04 | 1976-01-20 | Nippon Electric Co | Handotaireezano seizohoho |
| US3969686A (en) * | 1975-03-26 | 1976-07-13 | Xerox Corporation | Beam collimation using multiple coupled elements |
| JPS5231691A (en) * | 1975-09-04 | 1977-03-10 | Fujitsu Ltd | Semiconductor luminous device |
| JPS5382281A (en) * | 1976-12-28 | 1978-07-20 | Nippon Telegr & Teleph Corp <Ntt> | Production of high liminance semiconductor device and its apparatus |
| US4309668A (en) * | 1978-02-20 | 1982-01-05 | Nippon Electric Co., Ltd. | Stripe-geometry double heterojunction laser device |
| DE2822146C2 (en) * | 1978-05-20 | 1982-11-25 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Heterostructure semiconductor laser diode and method for manufacturing a heterostructure semiconductor diode |
| US4236296A (en) * | 1978-10-13 | 1980-12-02 | Exxon Research & Engineering Co. | Etch method of cleaving semiconductor diode laser wafers |
| US4237601A (en) * | 1978-10-13 | 1980-12-09 | Exxon Research & Engineering Co. | Method of cleaving semiconductor diode laser wafers |
| JPS6041478B2 (en) * | 1979-09-10 | 1985-09-17 | 富士通株式会社 | Manufacturing method of semiconductor laser device |
| NL8101409A (en) * | 1981-03-23 | 1982-10-18 | Philips Nv | SEMICONDUCTOR LASER WITH AT LEAST TWO RADIATION BEAMS, AND METHOD OF MANUFACTURING THESE. |
| US4352835A (en) * | 1981-07-01 | 1982-10-05 | Western Electric Co., Inc. | Masking portions of a substrate |
| US4539743A (en) * | 1983-11-28 | 1985-09-10 | At&T Bell Laboratories | Production of semiconductor structures with buried resistive or conductive regions by controlled ion bombardment and heat treatment |
-
1981
- 1981-09-02 NL NL8104068A patent/NL8104068A/en not_active Application Discontinuation
-
1982
- 1982-08-26 CA CA000410176A patent/CA1181514A/en not_active Expired
- 1982-08-27 US US06/412,052 patent/US4558448A/en not_active Expired - Lifetime
- 1982-08-30 EP EP82201063A patent/EP0073548B1/en not_active Expired
- 1982-08-30 DE DE8282201063T patent/DE3263763D1/en not_active Expired
- 1982-09-01 JP JP57152475A patent/JPS5852894A/en active Granted
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1985
- 1985-09-23 US US06/779,172 patent/US4670966A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0231868B2 (en) | 1990-07-17 |
| DE3263763D1 (en) | 1985-06-27 |
| JPS5852894A (en) | 1983-03-29 |
| US4558448A (en) | 1985-12-10 |
| EP0073548A1 (en) | 1983-03-09 |
| EP0073548B1 (en) | 1985-05-22 |
| NL8104068A (en) | 1983-04-05 |
| US4670966A (en) | 1987-06-09 |
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