Abstract: In the vapor phase epitaxy fabrication of semiconductor devices and in particular semiconductor lasers, the deposition body on which a particular layer of the laser is to be grown is preheated to a temperature about 40.degree. to 60.degree. C. lower than the temperature at which deposition occurs. It has been discovered that by preheating at this lower temperature there is reduced thermal decomposition at the deposition surface, especially for semiconductor materials such as indium gallium phosphide and gallium arsenide phosphide. A reduction in thermal decomposition reduces imperfections in the deposition body in the vicinity of the deposition surface, thereby providing a device with higher efficiency and longer lifetime.

Abstract: A thin coating of carbon is used as a mask to define regions of a crystalline material of the group III-V compounds. A carbon mask is coated on portions of a surface of a substrate and the masked substrate contacted with the group III-V material to deposit the crystalline material only on the portions of the surface of the substrate not covered with the masking coating. The group III-V material will not be deposited on the carbon coating, since it is incapable of nucleating the growth of the crystalline material. Accordingly, a defined region of the crystalline material is formed. The carbon masking coating can also be used as a mask for etching cavities or recesses in a substrate of the group III-V material.

Abstract: A substrate of single crystalline gallium arsenide has on a surface thereof a layer of single crystalline indium gallium phosphide. A layer of single crystalline gallium arsenide is on the indium gallium phosphide layer and a work function reducing material is on the gallium arsenide layer. The substrate has an opening therethrough exposing a portion of the indium gallium phosphide layer.