Abstract: A semiconductor device includes a very low dopant impurity concentration InGaAs active layer in which a two-dimensional electron gas is produced, the active layer being disposed on a semiconductor substrate; a very low dopant impurity concentration spacer layer contacting the active layer at a first surface and having an electron affinity smaller than the electron affinity of the active layer; and a very thin InGaAs electron supply layer having a high n type dopant impurity concentration and contacting the spacer layer opposite the active layer. Degradation of device characteristics due to heating of the device is reduced with a result that a thermally stable and highly reliable semiconductor device is easily realized.

Abstract: A heterojunction bipolar transistor includes a multiquantum barrier structure as part of the collector and contacting the base. The MQB has an energy band structure in which the height of the effective potential barrier of the MQB increases in steps from the base into the collector. Therefore, an electric field in the collector in the vicinity of the base-collector interface is relaxed and intervalley scattering of electrons is suppressed whereby a reduction in electron mobility due to the intervalley scattering is suppressed, reducing transit time of electrons in the collector.

Abstract: A semiconductor laser includes a first conductivity type semiconductor substrate; a first conductivity type semiconductor first cladding layer disposed on the substrate; a semiconductor active layer disposed on the first cladding layer; a second conductivity type semiconductor second cladding layer disposed on the active layer; a current concentration and collection structure for confining current flow to part of the active layer including a second conductivity type ridge structure disposed on the second cladding layer, a first conductivity type semiconductor current blocking layer disposed directly on the second cladding layer and adjacent to and contacting the ridge structure, the ridge structure including a semiconductor etch stopping layer different in composition from and disposed on the second cladding layer and a second conductivity type semiconductor third cladding layer disposed on and different in composition from the etch stopping layer, and a second conductivity type semiconductor transition layer

Abstract: A semiconductor structure for a light-interactive semiconductor device includes first and second crystalline semiconductor cladding layers having a first lattice constant and a strained superlattice structure disposed in contact with and between the first and second cladding layers and including alternating first crystalline semiconductor quantum barrier layers having a first and second crystalline semiconductor quantum well layers having a second energy band gap less than the first energy band gap and a third lattice constant wherein the first lattice constant is approximately equal to the average of the second and third lattice constants and the second lattice constant differs from the third lattice constant by at least 0.5 percent of the second lattice constant.