High Resistivity GaAs Epilayers by Oxygen Doping

摘要

During the first year of research our OMVPE system has been retrofitted with acharcoal exhaust scrubber, toxic gas detector, and process gas delivery system. All components have been fully tested and calibrated for GaAs deposition. High quality undoped GaAs epilayers have been deposited with following characteristics: specular morphology, low free carrier concentration ( p = 1 Xl0 to the 15th power cm-3) and high mobility (4,000 cm2/Vs at 77K). The dominant acceptor is carbon originating from gallium source as determined by the high resolution photoluminescence. Doping of GaAs epilayers with dimethylaluminum methoxide resulted in incorporation of both oxygen and aluminum in concentrations up to 5x10 to the 18th power 018 per cubic centimeter and 7x10 to the 19th power 019 per cubic centimeter respectively. Oxygen concentration increases rapidly with decreasing deposition temperature. Heavily oxygen doped layers (obtained either by high DMAIMO flow or growth at temperatures below 600 deg C) are highly resistive and exhibit extremely low carrier lifetime. Photoluminescence measurements detected new luminescence bands in 85G1000 nm range which are assigned to deep oxygen induced traps.