Growth by molecular beam epitaxy and characterization of high purity GaAs and AlGaAs

We report on the growth by molecular beam epitaxy of high-quality GaAs and Al_xGa_1-xAs (x≲0.43), and discuss the effect of system parameters on material quality. The highest Hall mobility in GaAs at 77 °K was 144 000 cm²/V sec, and the photoluminescence spectra of undoped layers exhibited a strong free exciton line and a much reduced carbon peak with no carbon-related defects. A slow growth process at a substrate temperature of 600 °C produced excellent Al_xGa_1-xAs whose luminescence spectrum showed a distinct excition peak 4 meV wide. This Al _xGa_1-xAs is compared to layers grown at a faster rate at substrate temperatures of 700 °C.