Carbon Doping of GaAs by OMVPE Using CC14: A Comparison of Gallium and Arsenic Precursors

Abstract

ABSTRACTThe carbon doping properties of GaAs with carbon tetrachloride as the dopant source were examined using trimethylgallium (TMGa) or triethylgallium (TEGa) as the gallium precursors and arsine or tertiarybutylarsine (TBAs) as the arsenic precursors. Secondary ion mass spectrometry (SIMS) and Hall measurements (van der Pauw method) were used to characterize the epitaxial GaAs:C layers. Very high C-doping concentrations (∼1020 cm−3) could be obtained with either TMGa and TEGa. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5–10 per mole of As precursor, over the temperature range examined (520°C - 700°C). Hydrogen at significant concentrations (0.5 – 6 × 1019 cm−3) was detected by SIMS in GaAs:C layers grown at ≤550°C utilizing all four combinations of Ga/As precursors and suggested the presence of electrically inactive C-H complexes. A post-growth anneal under helium at 550°C for 60s of these samples resulted in a 50–100% increase in hole concentration by driving out the hydrogen.