HETEROGENEOUS SEMICONDUCTOR STRUCTURE WITH COMPOSITION GRADIENT AND METHOD FOR PRODUCING SAME

摘要

1523056 Semiconductor devices GOSUDARST N I I PROEKT INST REDKUMETALLICHE PROMYSHLEN GIREDMET 9 Aug 1976 33012/76 Heading H1K A heterogeneous structure, e.g. for use in lasers and photoelectric cells comprises a monocrystalline substrate, a main semiconductor layer consisting of a doped solid solution AB x C 1-x (0#x#1) of the binary compounds AB and AC, the value of x decreasing monotonically along an axis extending between opposite side surfaces of the layer, and disposed between the main layer and substrate a doped transition layer of the same solid solution through the thickness of which x varies from the value in the adjacent part of the main layer to a constant value adjacent the substrate providing the optimum lattice constant matching therewith. Such a structure is formed by a gas transport reaction or evaporation of the compounds to the substrate from a source consisting of parallel strips of discretely different compositions disposed parallel and in close proximity thereto. The transition layer is formed by deposition while moving the source slowly into a position in register with the substrate along a path normal to the strips, and the main layer by continuing deposition with the strips in register. An additional layer of the same composition as the lower face of the transition layer may be deposited between it and the substrate from a further strip of the source. The relationship between source-substrate spacing and strip width is preferably such that lateral diffusion in the source-substrate gap causes the composition gradient in the layers to be continuous. The use of solid solutions consisting of pairs of binary A III B V , A II B VI or A IV B VI compounds in conjunction with substrates of such binary compounds, germanium, sapphire, beryllia or magnesia is suggested, the minimum transition layer thickness depending on the degree of lattice mismztch between main layer and substrate. Methods of making structures with main layers of GaAs x P 1-x , InAs x P 1-x , CdS x Se 1-x and Pb x Sn 1-x Te for incorporation in PN junction lasers or photocells for various wavelength bands, the wavelength of emission or peak photosensitivity of which are adjustable within a band, are described in detail. A pressure sensor sensitive over a wide range of pressures is formed on a (111) AsŒ31 oriented semi insulating GaAs substrate by depositing a GaAs additional layer, a graded GaAs x P 1-x semi insulating transition layer doped with Fe and Te, and a Te doped main layer of the composition shown, to opposite ends of which gold wires are attached by In-Sn solder. The source in this case has separate sets of iron doped and iron free strips for production of the transition and main layers, incorporation of iron in the latter from the iron doped strips and a source of iron in the reaction tube being avoided by reversal of the gas flow after the transition layer has been deposited.