Abstract: A photodetector comprising a light absorptive region, a wide bandgap region adjacent to the light absorptive region and a region of a first conductivity type extending through the wide bandgap region into the light absorptive region is improved by the incorporation of a lattice matched, intermediate bandgap region between the wide bandgap region and the light absorptive region. The p-n junction lies in the intermediate bandgap region in proximity to the interface thereof with the light absorptive region. The quantum efficiency of the disclosed device is significantly improved over prior art devices.

Abstract: The fabrication of a layer of a III-V semiconductor material by vapor phase epitaxy is improved by precoating the walls of the deposition chamber in a suitable apparatus with the desired material. The coating of the deposition chamber is continued until the material being deposited is depth-uniform and of the same composition as the desired layer. Material then deposited on the substrate is free of depth compositional gradient. In a further improvement, the walls of the deposition chamber of the apparatus are roughened, thus providing nucleation sites for the growing coating and substantially reducing the time required to precoat the walls of the deposition chamber.

Abstract: A photodetector includes a cap layer over an absorptive layer with the P-N junction formed in the absorptive layer by diffusion of conductivity modifiers from the cap layer. If this diffusion extends too far into the absorptive layer, the detector is rendered useless. The invention includes a photodetector with a buffer layer between the absorptive and cap layers. The concentration of conductivity modifiers is substantially constant in the cap layer, decreases with distance in the buffer layer from the cap layer and extends into the absorptive layer. The invention also includes a method of making this device which includes the steps of forming a buffer layer over the absorptive layer, forming a cap layer over the buffer layer and diffusing the opposite type conductivity modifiers from the cap layer into the buffer and absorptive layers.

Abstract: A thickness monitor useful in deposition or etching reactor systems comprising a crystal-controlled oscillator in which the crystal is deposited or etched to change the frequency of the oscillator. The crystal rests within a thermally conductive metallic housing and arranged to be temperature controlled. Electrode contacts are made to the surface primarily by gravity force such that the crystal is substantially free of stress otherwise induced by high temperature.