COMPARISON OF GALLIUM AND ARSENIC PRECURSORS FOR GAAS CARBON DOPING BY ORGANOMETALLIC VAPOR-PHASE EPITAXY USING CCL4

The carbon doping properties of GaAs grown by low pressure (30 Torr) organometallic vapor phase epitaxy at 520-700-degrees-C with CCl4 as the dopant precursor were compared for the four possible combinations of trimethylgallium (TMGa), triethylgallium (TEGa), arsine (AsH3), and tertiarybutylarsine (TBAs). Secondary ion mass spectrometry (SIMS), Hall measurements, and infrared absorption were used to characterize the GaAs:C layers. Very high C-doping concentrations (approximately 10(20) cm-3) could be obtained using either TMGa or TEGa and AsH3. 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 growth temperature range examined. Hydrogen at significant concentrations (1-6 X 10(19) cm-3) was detected by SIMS in GaAs: C layers grown at less-than-or-equal-to 550-degrees-C utilizing all four combinations of Ga/As precursors. The existence of electrically inactive C-H complexes was confirmed by observation of the C-H stretching mode at 2635 cm-1. A post-growth anneal under helium at 150-degrees-C for 60 s removed the C-H pairs resulting in a 50%-100% increase in hole concentration. There was no change in the hole concentration for GaAs:C grown at greater-than-or-equal-to 600-degrees-C, indicating negligible hydrogen passivation.