A nitride semiconductor device includes a GaN substrate having a single-crystal GaN layer at least on its surface and plurality of device-forming layers made of nitride semiconductor. The device-forming layer contacting the GaN substrate has a coefficient of thermal expansion smaller than that of GaN,...http://www.google.com.au/patents/US7083996?utm_source=gb-gplus-sharePatent US7083996 - Nitride semiconductor device and manufacturing method thereof
