Native defects in low temperature GaAs and the effect of hydrogenation

GaAs grown at low temperatures by MBE has been doped with shallow impurities to approx.10¹⁹ cm^-3. A layer doped with Be acceptors was completely compensated and the simultaneous detection of As_Ga ⁰ and As_Ga ⁺ confirmed that the Fermi level was close to midgap and that compensation was partly related to As_Ga defects. There was no evidence for the incorporation of V_Ga in this layer. For Si-doped samples, more than 80% of the donors were compensated and the detection of Si_Ga-V_Ga pairs by infrared localized vibrational mode (LVM) spectroscopy indicated that V_Ga were at least partly responsible. Increasing the Si concentration suppressed the incorporation of As_Ga. Exposure of the Be-doped layer to a hydrogen plasma, generated a LVM near 2000 cm^-1 which may be the stretch mode of a As_Ga-H-V_As defect complex. For Si-doped layers, two stretch modes at 1764 cm^-1 and 1773 cm^-1 and a wag mode at 770 cm^-1 relating to a H-defect complex were detected and we argue that the complex could be a passivated As antisite. The detection of characteristic hydrogen-native defect LVMs may provide a new method for the identification of intrinsic defects.