CA1067989A - Semiconductor laser with a light guide - Google Patents
Semiconductor laser with a light guideInfo
- Publication number
- CA1067989A CA1067989A CA266,842A CA266842A CA1067989A CA 1067989 A CA1067989 A CA 1067989A CA 266842 A CA266842 A CA 266842A CA 1067989 A CA1067989 A CA 1067989A
- Authority
- CA
- Canada
- Prior art keywords
- active region
- light guide
- laser
- mesa
- xalxas
- 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
Links
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
- H01S5/02—Structural details or components not essential to laser action
- H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
-
- 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
- H01S5/227—Buried mesa structure ; Striped 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
- H01S5/22—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
- H01S5/227—Buried mesa structure ; Striped active layer
- H01S5/2275—Buried mesa structure ; Striped active layer mesa created by etching
Abstract
SEMICONDUCTOR LASER WITH A LIGHT GUIDE
Abstract of the Disclosure In a semiconductor laser with a light guide (wave guide), an active region constituting a Fabry-Perot cavity is formed in a mesa part on a semiconductor substrate. A mixed crystal composition fills mesa-etched hollows to constitute a light guide. The improvement is that the active region consists of, Ga1-xAlxAs (0?x<1) and the mixed crystal of the light guide consists of GaAs1-yPy (0<y<1), or Ga1-zAlzAs (0<x<z<1), having a high (for instance, 104.OMEGA.cm). specific resistivity compared with that of the active region. The value of y or z is selected to be smallest at the level to receive light from the cavity, i.e. at the level of the active region, to con-centrate the light, and the energy gap of the mixed crystal composition is selected to be larger than that of the active region so that light loss in the light guide is decreased.
Abstract of the Disclosure In a semiconductor laser with a light guide (wave guide), an active region constituting a Fabry-Perot cavity is formed in a mesa part on a semiconductor substrate. A mixed crystal composition fills mesa-etched hollows to constitute a light guide. The improvement is that the active region consists of, Ga1-xAlxAs (0?x<1) and the mixed crystal of the light guide consists of GaAs1-yPy (0<y<1), or Ga1-zAlzAs (0<x<z<1), having a high (for instance, 104.OMEGA.cm). specific resistivity compared with that of the active region. The value of y or z is selected to be smallest at the level to receive light from the cavity, i.e. at the level of the active region, to con-centrate the light, and the energy gap of the mixed crystal composition is selected to be larger than that of the active region so that light loss in the light guide is decreased.
Description
7'38~3 This invention relates to a semiconductor laser with a 11ght guide wherein a light guide part ~f the laser is coupled to a light output part of the laser.
Semiconductor lasers are useful as light sources for integrated optical circuits, wherein matching between the light guide and the end parts of the active regions, namely the Fabry-Perot cavities, are important. To attain satisfactory matching, it is recommended that the laser and the light guide be a united structure.
Such a united or integrated structure of a semiconductor laser and a light guide (wave guide) is described in an article entitled "Integrated GaAs-AlGaAs double-heterostructure lasers" by C.E. Hurwitz et al in "Applied Physics Letters", -Vol. 27, ~o. 4, 15 August 1975, pages 241-243.
Before describing this prior art the figures of the drawings herein will be listed:
- Fig. 1 is a sectional sideview of a semiconductor laser with a light guide, according to tXe prior art as described in said article;
F1g. 2(a) is a sectional sideview of a semiconductor laser with a light guide, according to one example of the present invention;
~Fig. 2(b~ is a plan view of Fig. 2(a);
Fig. 2(c) is a plan view of a modified example; and - i . , : .
~Fig. 3(a), (b~ and (c)are respectively an enlarged sideview of a part of Fig. 2(a), a graph showing distribution af the y value of the composition GaAsl P of the light guid~, and a graph showing the distribution of relative refractive index of the light gulde.
~In the prior art article, as shown in Fig. 1 by a sectional : . .
view, a semiconductor laser~comprises a laser part 10 and a ~
~: ~ , . :
~ ' ~
.
~L~6~7989 ... .
light guide part 11 on a single wa~er. The laser part is made by sequential epitaxial growths on a substrate 5 of n-type GaAs~ of a first layer 1 of n-type GaO 7Alo 3As, a second layer 2, i.e., an active region of p--type GaAs, a third layer 3 of p-type GaO 7Alo 3As and a fourth layer 4 of p-type GaAs, and finally attaching electrodes 6 and 7. The light guide (wave guide) part 10 is made by forming n-type GaAs of low impurity concentration in mesa-etchecl hollow parts of the laser structure. The laser and light guide parts are isolated from each other by insulation films 8 s-lch as SiO2.
In this prior laser the light guide part 10 is several times thicker than the active region 2, and accordingly, the light from the active region 2 diverges at a wide angle of several tens of degrees, thereby making convergence of the light difficult.
- The principal object of the present invention is to pro-vide a semiconductor laser with a light guide, wherein light divergence in the light guide is small and light loss is low.
This object is achieved by providing a semiconductor
Semiconductor lasers are useful as light sources for integrated optical circuits, wherein matching between the light guide and the end parts of the active regions, namely the Fabry-Perot cavities, are important. To attain satisfactory matching, it is recommended that the laser and the light guide be a united structure.
Such a united or integrated structure of a semiconductor laser and a light guide (wave guide) is described in an article entitled "Integrated GaAs-AlGaAs double-heterostructure lasers" by C.E. Hurwitz et al in "Applied Physics Letters", -Vol. 27, ~o. 4, 15 August 1975, pages 241-243.
Before describing this prior art the figures of the drawings herein will be listed:
- Fig. 1 is a sectional sideview of a semiconductor laser with a light guide, according to tXe prior art as described in said article;
F1g. 2(a) is a sectional sideview of a semiconductor laser with a light guide, according to one example of the present invention;
~Fig. 2(b~ is a plan view of Fig. 2(a);
Fig. 2(c) is a plan view of a modified example; and - i . , : .
~Fig. 3(a), (b~ and (c)are respectively an enlarged sideview of a part of Fig. 2(a), a graph showing distribution af the y value of the composition GaAsl P of the light guid~, and a graph showing the distribution of relative refractive index of the light gulde.
~In the prior art article, as shown in Fig. 1 by a sectional : . .
view, a semiconductor laser~comprises a laser part 10 and a ~
~: ~ , . :
~ ' ~
.
~L~6~7989 ... .
light guide part 11 on a single wa~er. The laser part is made by sequential epitaxial growths on a substrate 5 of n-type GaAs~ of a first layer 1 of n-type GaO 7Alo 3As, a second layer 2, i.e., an active region of p--type GaAs, a third layer 3 of p-type GaO 7Alo 3As and a fourth layer 4 of p-type GaAs, and finally attaching electrodes 6 and 7. The light guide (wave guide) part 10 is made by forming n-type GaAs of low impurity concentration in mesa-etchecl hollow parts of the laser structure. The laser and light guide parts are isolated from each other by insulation films 8 s-lch as SiO2.
In this prior laser the light guide part 10 is several times thicker than the active region 2, and accordingly, the light from the active region 2 diverges at a wide angle of several tens of degrees, thereby making convergence of the light difficult.
- The principal object of the present invention is to pro-vide a semiconductor laser with a light guide, wherein light divergence in the light guide is small and light loss is low.
This object is achieved by providing a semiconductor
2~ laser with a light guide comprising (a) a laser part which includes an active region on a monollthic semiconductor wafer, and ;
(b) a light guide part Eormed on said semiconductor wafer and optically coupled to said laser part, said light guide!part having a distribution of refractive index such that said index is largest in a central plane in a path of laser light emitted from said active region and having a high resistivity in comparison with layers of said laser part.
The invention also relates to a method of making a semi-conductor laser with a light guide, comprising the steps of , (a~ forming by sequential epitaxial growths on a semi-conductor substrate an active region and at least upper and :~ .
;, ~
.
;7989 `lower neighboring layers which form heterojunctions to define said active region, (b) etching at least said active region and said neighbor- -ing layers to form an unetched mesa part including said active region and said neighboring regions and to form etched hollow parts on both sides o,f said mesa part, (c) forming insulation films at least on end faces of said mesa-part, and (d) forming at least one light guide part by filling said hollow parts with a mixed crystal composition having a re-fractive index that is largest at a level aligned with a central plane of the active region, said mixed crystal, comp-osition having a high resistivity in comparison with the resistivities of the other layers in said mesa part.
Fig. 2(a) and Fig. 2(b) show sectional side and plan views of one example of the present invention. The la'ser part 10 of this example is made as follows:
On a semiconductor substrate 5 of n-type GaAs, a first layer of 1 of 2~m thick n-type Ga~ 7Alo 3As, a second layer ~, 2 of 0.2~m thick p-type GaAs, a third layer 3 of l~m thick '~
p-type GaO 7Alo 3As and a fourth layer 4 of l~m thick p -type GaAs are ~ormed by sequential epitaxial growths. Then a =esa-etching from the fourth layer 4 to an upper part of the substrate 5 is carried out to form mesa-etched hollow parts 9.
Thus, the laser part comprises an active region, i.e. a ~ ' '' resonant cavity 2, of p-type GaAs. The bottom of the mesa-etched hollows may be in the first layer 1 instead of the abovementioned structure where the bottom of the mesa-etched , hollows are in the substrate. Insulation films 8 of SiO2 are formed on~both end walls of the laser part 10 by known thermal decomposit~ion of silane in an oxidizing atmosphere or by ~4~ ' ;' : ', ' , ' : :. .. ... . ... ,..... .. ,...... .... , . . ,, ., : .
79~39 known chemical vapor deposition of S102. Instead of SiO2, Si3N4 may be used for the insulation films.' These insulation fllms 8 have lower refractive indices than that of the active .
region 2, and accordingly the insulation films function as mirrors of the resonance cavity.
A high resistivity layer 11 of GaAsl P is filled in the mesa-etched hollow parts 9 in such a manner that the top face of the layer 11 and the fourth layer 4 are flush ~ith each other. The resistivity of the layer 11 should be sig-nificantly higher, for instance about 104ncm, than the reslst-ivity of the layers in the laser part 10. The high resistivity layer 11 forms light guldes coupled to the end faces of the laser part 10 so as to receive lasing light therefrom.
The value y which represents the amount of phosphorous is controlled in the manner shown in Fig. 3(a) and Fig. 3(b), `i.e. to be smallest at the depth level with the central part ~ -of the active reglon 2, becomlng larger and eventually uniform moving upwards and downwards from this central part. As a consequence of this variation of the y value, i.e. the phos-phorous component, the refractlve index of the light guide 11 -is made to have a square function distribution as seen in Flg. 3(c). Llght beams lased in the laser part and emitted from the active part 2 through the transparent SiO2 films .
- 8 1nto ehe light guide 11 are 'thus converged or concentrated by me~ns of this refractive lndex distrlbution. Thus, the : ' ! ' lighe is concentrated wlthin a thin area of several ~m thickness optlcally coupled to the ends of the active layer with the insulation film between. Since the light transmitted through the~light guide parts;ll is so concentrated, losses are small ~30 and~ the llght is comparativsly undistorted.
By s~electing the~value y to be O<y, namely by including at least a~small amount of phosphorous even at the level of ~5~~
~: , . , : , ~: :
~L0~i~7~38~3 the central part of the active region 2, the energy gap of the llght guide part 11 can be made larger ~han that of the active region 2, whereby light absorption in the light guide is sub-stantially eliminated.
In practice the value y can be varied within the range of O<y<l. The optimum range for y is O<y<0.3, since the crystal strain is very small for this range. As mentioned,it is preferable to arrange the energy gap of the light guide 11 to be larger than that of the active region 2.
In a modification a part of the Ga in the GaAs of the active region 2 is replaced by Al to form an active region of Gal Al As (wherein O<x<l). 5~ , In a further modification the light guide can be made with Gal zAl As wherein O<z<x<l, instead of the abovementioned GaAsl yP . In such a combination of active region and light guide, the refractive index as well as the energy gap of the light guide should be made larger than those of the active ~
region, thereby attaining good convergence as well as a small ;
àbsorption of light in the light g~uide.
To summarise for the combination of an activè region of ~Gal xAl As (whereln O<x<l) and a light guide selected from the group of GaAsl P (wherein O<y<l) and Gal zAl As (wherein O<x<z<l) the distribution of the refractive index is such that it is largeet at the~ level of the center of the active ~-region.
~ Fig. 2(c) shows a plan view of another example wherein the meRa-etching is made on all side faces of the epltaxially :
grown layers, the sectional sideview being identical to Fig. 2(a).
,, In this example, the mesa part and hence the active region 2 30 is formed as a strip of 20~m width and 300~m length in plan - ~ -view, with insulation film 8 =urrounding all its four side ~ -6 :: ~ :
~, , , . ' .
1C~6'~89 faces, with a light guide area 11 surrounding all these side faces.
The siæes of the mesa parts of the lasers of Fig. 2(b) and Fig. 2(c) should be chosen in accordance with the required output and lasing mode.
In the case of a strip shaped mesa part, the light guide part-s can also be designed as strips having the same width as the mesa part. Although the strip type laser shown in Fig. ~(c) has insulation film 8 on four sides of the mesa part, the in-sulation film on the two longer faces can be omitted, since theGaAsl P or Gal Al As of the light guide 11 is of very high resistivity and hence permits substantially no leakage current.
,~ .
Such a device can be made as follows:
First, by means of a known sequential epitaxial growth method9 the first layer 1 of n-type GaO 7Alo 3As of 2~m tnickness the second layer 2 of p-type GaAs of 0.2~m thickness, the third layer 3 of p-type GaO 7Alo 3As of l~m thickness, and the fourth layer 4 of p+-type GaAs of l~m thickness are sequentially formed on the substrate 5 of n-type GaAs. Either a vapor phase epitaxial growth method or a liquid phase epitaxial growth method can be used.
The wafer is then etched to form the mesa hollow parts while retaining the mesa part. The etching is made with a kno~wn etchant, e.g. a mixed solution of sulfuric acid, hydrogen peroxide~and water, since the wafer is made of GaAs and GaO 7Alo 3As. The etching is made from the top layer, nàmely the fourth layer to the bottom layer, namely the substrate 5, and the;etching should be made a~ least up to a certain level of the fi~rst layer 1. In other wordæ, the bottom of the etched hollow~parts may be either in the first layer;l or in the substrate 5~.~ During the mesa-etchi~ng, the depth of the mesa-~: ~ . - :
~: . : :: ~ .
-?- ' ~
.
:
:: :
'7~89 etched hollow should be well controlled in order to control accurately the depth of the smallese y ralue part in the next step of forming the light guide parts 11 of high resistivity GaAsl P , in order that the level of the smallest y can be aligned with the central part of the active region, i.e., the second layer 2. ~y employing a known chemical vapor deposition or a known molecular beam epitaxial growth method in forming the high resistivity GaAsl P layer, the growth speed can be controlled very accurately. For instance, by employing a thermal decomposition and reaction at 630 C of a mixed gas consisting of gases of Ga(CE3)3, AsH3 and PH3, a layer of sufficiently high resistivity of 105Qcm is formed at a growth speed of 0.6~m per minute. During the growth process, the ratio of AsH3 to PH3 is controlled in such a manner that the value of y is made smallest at the level of the central part of the active region 2, gradually larger above and below this level and uniform once a distance of several ~m has been achieved. This control utilises the accurately measured depth of the mesa-etched hollow parts.
Finally, a palr of electrodes 6 and 7 of Au films are attached by a known vacuum deposition method to the top and bottom face of the laser part. The semiconductor laser with the light guide ll is then complete.
When Gal zAl As is employed for the high resistivity light guide parts 11 its manner of maklng can be similar to the above method.
~ ~y reason of the small light loss and good ligh~ concen~
- tration with consequent efficient light transmission~ the pres~ent construction is~suitable as a light source for integrated optical circuits. Moreover~ the method of manu-facture is easy and suitable for mass production.
: ~ ,: , ~ ' ' ' ' "
~ . ~
~ -8- ~
(b) a light guide part Eormed on said semiconductor wafer and optically coupled to said laser part, said light guide!part having a distribution of refractive index such that said index is largest in a central plane in a path of laser light emitted from said active region and having a high resistivity in comparison with layers of said laser part.
The invention also relates to a method of making a semi-conductor laser with a light guide, comprising the steps of , (a~ forming by sequential epitaxial growths on a semi-conductor substrate an active region and at least upper and :~ .
;, ~
.
;7989 `lower neighboring layers which form heterojunctions to define said active region, (b) etching at least said active region and said neighbor- -ing layers to form an unetched mesa part including said active region and said neighboring regions and to form etched hollow parts on both sides o,f said mesa part, (c) forming insulation films at least on end faces of said mesa-part, and (d) forming at least one light guide part by filling said hollow parts with a mixed crystal composition having a re-fractive index that is largest at a level aligned with a central plane of the active region, said mixed crystal, comp-osition having a high resistivity in comparison with the resistivities of the other layers in said mesa part.
Fig. 2(a) and Fig. 2(b) show sectional side and plan views of one example of the present invention. The la'ser part 10 of this example is made as follows:
On a semiconductor substrate 5 of n-type GaAs, a first layer of 1 of 2~m thick n-type Ga~ 7Alo 3As, a second layer ~, 2 of 0.2~m thick p-type GaAs, a third layer 3 of l~m thick '~
p-type GaO 7Alo 3As and a fourth layer 4 of l~m thick p -type GaAs are ~ormed by sequential epitaxial growths. Then a =esa-etching from the fourth layer 4 to an upper part of the substrate 5 is carried out to form mesa-etched hollow parts 9.
Thus, the laser part comprises an active region, i.e. a ~ ' '' resonant cavity 2, of p-type GaAs. The bottom of the mesa-etched hollows may be in the first layer 1 instead of the abovementioned structure where the bottom of the mesa-etched , hollows are in the substrate. Insulation films 8 of SiO2 are formed on~both end walls of the laser part 10 by known thermal decomposit~ion of silane in an oxidizing atmosphere or by ~4~ ' ;' : ', ' , ' : :. .. ... . ... ,..... .. ,...... .... , . . ,, ., : .
79~39 known chemical vapor deposition of S102. Instead of SiO2, Si3N4 may be used for the insulation films.' These insulation fllms 8 have lower refractive indices than that of the active .
region 2, and accordingly the insulation films function as mirrors of the resonance cavity.
A high resistivity layer 11 of GaAsl P is filled in the mesa-etched hollow parts 9 in such a manner that the top face of the layer 11 and the fourth layer 4 are flush ~ith each other. The resistivity of the layer 11 should be sig-nificantly higher, for instance about 104ncm, than the reslst-ivity of the layers in the laser part 10. The high resistivity layer 11 forms light guldes coupled to the end faces of the laser part 10 so as to receive lasing light therefrom.
The value y which represents the amount of phosphorous is controlled in the manner shown in Fig. 3(a) and Fig. 3(b), `i.e. to be smallest at the depth level with the central part ~ -of the active reglon 2, becomlng larger and eventually uniform moving upwards and downwards from this central part. As a consequence of this variation of the y value, i.e. the phos-phorous component, the refractlve index of the light guide 11 -is made to have a square function distribution as seen in Flg. 3(c). Llght beams lased in the laser part and emitted from the active part 2 through the transparent SiO2 films .
- 8 1nto ehe light guide 11 are 'thus converged or concentrated by me~ns of this refractive lndex distrlbution. Thus, the : ' ! ' lighe is concentrated wlthin a thin area of several ~m thickness optlcally coupled to the ends of the active layer with the insulation film between. Since the light transmitted through the~light guide parts;ll is so concentrated, losses are small ~30 and~ the llght is comparativsly undistorted.
By s~electing the~value y to be O<y, namely by including at least a~small amount of phosphorous even at the level of ~5~~
~: , . , : , ~: :
~L0~i~7~38~3 the central part of the active region 2, the energy gap of the llght guide part 11 can be made larger ~han that of the active region 2, whereby light absorption in the light guide is sub-stantially eliminated.
In practice the value y can be varied within the range of O<y<l. The optimum range for y is O<y<0.3, since the crystal strain is very small for this range. As mentioned,it is preferable to arrange the energy gap of the light guide 11 to be larger than that of the active region 2.
In a modification a part of the Ga in the GaAs of the active region 2 is replaced by Al to form an active region of Gal Al As (wherein O<x<l). 5~ , In a further modification the light guide can be made with Gal zAl As wherein O<z<x<l, instead of the abovementioned GaAsl yP . In such a combination of active region and light guide, the refractive index as well as the energy gap of the light guide should be made larger than those of the active ~
region, thereby attaining good convergence as well as a small ;
àbsorption of light in the light g~uide.
To summarise for the combination of an activè region of ~Gal xAl As (whereln O<x<l) and a light guide selected from the group of GaAsl P (wherein O<y<l) and Gal zAl As (wherein O<x<z<l) the distribution of the refractive index is such that it is largeet at the~ level of the center of the active ~-region.
~ Fig. 2(c) shows a plan view of another example wherein the meRa-etching is made on all side faces of the epltaxially :
grown layers, the sectional sideview being identical to Fig. 2(a).
,, In this example, the mesa part and hence the active region 2 30 is formed as a strip of 20~m width and 300~m length in plan - ~ -view, with insulation film 8 =urrounding all its four side ~ -6 :: ~ :
~, , , . ' .
1C~6'~89 faces, with a light guide area 11 surrounding all these side faces.
The siæes of the mesa parts of the lasers of Fig. 2(b) and Fig. 2(c) should be chosen in accordance with the required output and lasing mode.
In the case of a strip shaped mesa part, the light guide part-s can also be designed as strips having the same width as the mesa part. Although the strip type laser shown in Fig. ~(c) has insulation film 8 on four sides of the mesa part, the in-sulation film on the two longer faces can be omitted, since theGaAsl P or Gal Al As of the light guide 11 is of very high resistivity and hence permits substantially no leakage current.
,~ .
Such a device can be made as follows:
First, by means of a known sequential epitaxial growth method9 the first layer 1 of n-type GaO 7Alo 3As of 2~m tnickness the second layer 2 of p-type GaAs of 0.2~m thickness, the third layer 3 of p-type GaO 7Alo 3As of l~m thickness, and the fourth layer 4 of p+-type GaAs of l~m thickness are sequentially formed on the substrate 5 of n-type GaAs. Either a vapor phase epitaxial growth method or a liquid phase epitaxial growth method can be used.
The wafer is then etched to form the mesa hollow parts while retaining the mesa part. The etching is made with a kno~wn etchant, e.g. a mixed solution of sulfuric acid, hydrogen peroxide~and water, since the wafer is made of GaAs and GaO 7Alo 3As. The etching is made from the top layer, nàmely the fourth layer to the bottom layer, namely the substrate 5, and the;etching should be made a~ least up to a certain level of the fi~rst layer 1. In other wordæ, the bottom of the etched hollow~parts may be either in the first layer;l or in the substrate 5~.~ During the mesa-etchi~ng, the depth of the mesa-~: ~ . - :
~: . : :: ~ .
-?- ' ~
.
:
:: :
'7~89 etched hollow should be well controlled in order to control accurately the depth of the smallese y ralue part in the next step of forming the light guide parts 11 of high resistivity GaAsl P , in order that the level of the smallest y can be aligned with the central part of the active region, i.e., the second layer 2. ~y employing a known chemical vapor deposition or a known molecular beam epitaxial growth method in forming the high resistivity GaAsl P layer, the growth speed can be controlled very accurately. For instance, by employing a thermal decomposition and reaction at 630 C of a mixed gas consisting of gases of Ga(CE3)3, AsH3 and PH3, a layer of sufficiently high resistivity of 105Qcm is formed at a growth speed of 0.6~m per minute. During the growth process, the ratio of AsH3 to PH3 is controlled in such a manner that the value of y is made smallest at the level of the central part of the active region 2, gradually larger above and below this level and uniform once a distance of several ~m has been achieved. This control utilises the accurately measured depth of the mesa-etched hollow parts.
Finally, a palr of electrodes 6 and 7 of Au films are attached by a known vacuum deposition method to the top and bottom face of the laser part. The semiconductor laser with the light guide ll is then complete.
When Gal zAl As is employed for the high resistivity light guide parts 11 its manner of maklng can be similar to the above method.
~ ~y reason of the small light loss and good ligh~ concen~
- tration with consequent efficient light transmission~ the pres~ent construction is~suitable as a light source for integrated optical circuits. Moreover~ the method of manu-facture is easy and suitable for mass production.
: ~ ,: , ~ ' ' ' ' "
~ . ~
~ -8- ~
Claims (7)
1. A semiconductor laser with a light guide comprising (a) a laser part which includes an active region on a monolithic semiconductor wafer, and (b) a light guide part formed on said semiconductor wafer and optically coupled to said laser part, said light guide part having a distribution of refractive index such that said index is largest in a central plane in a path of laser light emitted from said active region and having a high resist-ivity in comparison with layers of said laser part.
2. A semiconductor laser of claim 1 wherein said laser part comprises a heterojunction of GaAs - Ga1-xAlxAs, with 0?x<1, between a said active region of Ga1-xAlxAs and a neighboring GaAs region, said light guide part being made of GaAs1-yPy, with 0<y<1, the value of y being smallest at said plane.
3. A semiconductor laser of claim 1 wherein said laser part comprises a heterojunction of GaAs - Ga1-xAlxAs, with 0?x<1, between a said active region of Ga1-xAlxAs and a neighboring GaAs region, said light guide part being made of Ga1-zAlzAs, with 0<x<z<1, the value of z being smallest at said plane.
4. A semiconductor laser of claim 2 wherein x=0 and 0<y<0.3.
5. A method of making a semiconductor laser with a light guide, comprising the steps of (a) forming by sequential epitaxial growths on a semi-conductor substrate an active region and at least upper and lower neighboring layers which form heterojunctions to define said active region, (b) etching at least said active region and said neigh-boring layers to form an unetched mesa part including said active region and said neighboring regions and to form etched hollow parts on both sides of said mesa part, (c) forming insulation films at least on end faces of said mesa-part, and (d) forming at least one light guide part by filling said hollow parts with a mixed crystal composition having a refractive index that is largest at a level aligned with a central plane of the active region, said mixed crystal comp-osition having a high resistivity in comparison with the resistivities of the other layers in said mesa part.
6. A method of claim 5, wherein said active region is Ga1-xAlxAs, with 0?x<1, and said mixed crystal is GaAs1-yPy, with 0<y<1.
7. A method of claim 5, wherein said active region is Ga1-xAlxAs, with 0?x<1, and said mixed crystal is Ga1-zAlzAs, with 0<x<z<1.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50145720A JPS5269285A (en) | 1975-12-05 | 1975-12-05 | Semiconductor laser device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067989A true CA1067989A (en) | 1979-12-11 |
Family
ID=15391559
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA266,842A Expired CA1067989A (en) | 1975-12-05 | 1976-11-30 | Semiconductor laser with a light guide |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4144503A (en) |
| JP (1) | JPS5269285A (en) |
| CA (1) | CA1067989A (en) |
| GB (1) | GB1547180A (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7903197A (en) * | 1979-04-24 | 1980-10-28 | Philips Nv | METHOD FOR MANUFACTURING AN ELECTROLUMINESCENT SEMICONDUCTOR DEVICE AND ELECTROLUMINESCENT SEMICONDUCTOR DEVICE MADE ACCORDING TO THE METHOD |
| JPS58140177A (en) * | 1982-02-16 | 1983-08-19 | Kokusai Denshin Denwa Co Ltd <Kdd> | Distributed feed-back type semiconductor laser |
| US4464762A (en) * | 1982-02-22 | 1984-08-07 | Bell Telephone Laboratories, Incorporated | Monolithically integrated distributed Bragg reflector laser |
| JPS59143109A (en) * | 1983-02-04 | 1984-08-16 | Sumitomo Electric Ind Ltd | Optical integrated circuit |
| US4758092A (en) * | 1986-03-04 | 1988-07-19 | Stanford University | Method and means for optical detection of charge density modulation in a semiconductor |
| US4804639A (en) * | 1986-04-18 | 1989-02-14 | Bell Communications Research, Inc. | Method of making a DH laser with strained layers by MBE |
| US4933302A (en) * | 1989-04-19 | 1990-06-12 | International Business Machines Corporation | Formation of laser mirror facets and integration of optoelectronics |
| JPH04145414A (en) * | 1990-10-08 | 1992-05-19 | Fujitsu Ltd | Optical waveguide type wavelength filter |
| US5872360A (en) * | 1996-12-12 | 1999-02-16 | Intel Corporation | Method and apparatus using an infrared laser based optical probe for measuring electric fields directly from active regions in an integrated circuit |
| US5904486A (en) * | 1997-09-30 | 1999-05-18 | Intel Corporation | Method for performing a circuit edit through the back side of an integrated circuit die |
| US6072179A (en) * | 1998-08-07 | 2000-06-06 | Intel Corporation | Method and apparatus using an infrared laser based optical probe for measuring voltages directly from active regions in an integrated circuit |
| US7602828B2 (en) * | 2006-11-13 | 2009-10-13 | Jds Uniphase Corporation | Semiconductor laser diode with narrow lateral beam divergence |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2152464B1 (en) * | 1971-09-16 | 1974-05-31 | Thomson Csf | |
| US3968564A (en) * | 1975-04-30 | 1976-07-13 | Northern Electric Company Limited | Alignment of optical fibers to light emitting diodes |
-
1975
- 1975-12-05 JP JP50145720A patent/JPS5269285A/en active Pending
-
1976
- 1976-11-30 CA CA266,842A patent/CA1067989A/en not_active Expired
- 1976-12-02 US US05/746,750 patent/US4144503A/en not_active Expired - Lifetime
- 1976-12-03 GB GB50534/76A patent/GB1547180A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1547180A (en) | 1979-06-06 |
| US4144503A (en) | 1979-03-13 |
| JPS5269285A (en) | 1977-06-08 |
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