Effect of Heat Treatment on Gallium Arsenide Crystals. I. Thermal Conversion in Excess Arsenic Vapor

Abstract

Undoped n -GaAs crystals grown from the melt have been heat-treated in a quartz ampoule under 3.4 Torr of arsenic vapor pressure at 650 to 800°C. The crystals were converted to p -type crystals by this heat treatment. Acceptor concentration in the crystals, which were in equilibrium with the ambient factors at temperature T , is expressed as 10 -2.8 exp (-0.6 eV/ k T ) per lattice site. The acceptors are initially formed at the crystal surface and then diffuse into the interior. Rate of junction migration has been measured, and analyzed, on an assumption that the formation rate of the acceptors (in flux) is proportional to the difference of the surface concentration from the equilibrium concentration. Results are: the formation rate constant k f (cm/sec)=10 -0.6 exp (-1.1 eV/ k T ) and the diffusion coefficient D (cm 2 /sec)=10 4.8 exp (-2.5 eV/ k T ). These results cannot be explained in terms of copper contamination alone and are suggestive of an influence of Ga vacancies.