Effect of Thermal Etching on GaAs Substrate in Molecular Beam Epitaxy

Abstract

Thermal etching of GaAs substrates prior to epitaxial growth by molecular beam epitaxy has been used to reduce carrier depletion at the substrate and epitaxial layer interface. The amount of carrier depletion between a Si-doped n-GaAs substrate and a Si-doped n-GaAs epitaxial film, measured by a C-V carrier profiling technique, was proved to decrease significantly with increased etched depth at a substrate temperature of 750°C. The origin of the carrier depletion is believed to be the carbon acceptor, from the results of C-V measurement and secondary ion mass spectrometory. Based on these results, thermal etching was successfully applied to semi-insulating GaAs substrates to improve mobility and sheet concentrations of two-dimensional electron gas in the selectively doped GaAs/N-Al_0.3Ga_0.7As heterostructures with very thin GaAs buffer layers (0.2 µm).