Low-dislocation indium-alloyed GaAs

Abstract

We have grown crystals of In-alloyed GaAs, In x Ga 1 - x As, by the LEC method from pyrolytic BN crucibles without the intentional addition of any donor or acceptor impurities. The values of x ranged from 0.0028 to 0.023, depending on the initial melt composition and the extent of solidification of the original melt when the sample crystallized. The values of x were determined by energy-dispersive X-ray analysis, Zeeman atomic absorption analysis, and photoluminescence measurement of the bandgap shift, the last method calibrated by neutron activation analysis. In the range of In content studied, the effective distribution coefficient of In between crystal and melt is 0.118. Dislocation density, revealed by KOH etching, decreases as x increases, approaching zero in some regions of the crystal cross section. The influence of metal-As stoichiometry is similar to the case of undoped and unalloyed GaAs, and operates through the same mechanisms. With sufficient As in the melt the alloy crystals are semi-insulating, but if the As content of the melt is too low initially or drops too low during growth, the crystal is low-resistivity p-type.