HEAVILY CARBON-DOPED GAALAS GROWN BY VACUUM CHEMICAL EPITAXY

Heavily p-doped GaAlAs layers have been grown on GaAs substrates by vacuum chemical epitaxy (VCE), using trimethylaluminum (TMA) as an aluminum source. Triethylgallium (TEG) and arsine were used as gallium and arsenic sources, respectively. Net carrier concentrations in the range 5×10 19-2×1020 cm- 3 and mobilities of ≅30-40 cm2/V s have been achieved. GaAlAs layers grown with triisobutylaluminum (TIBAl) as aluminum source have shown residual concentrations almost three orders of magnitude smaller, thus indicating a greater carbon incorporation associated to the use of TMA. The residual dopant concentration can be reduced by using a higher AsH3 flow or introducing H2 in a VCE reactor during growth, due to the easier methyl removal in these conditions.