Trap gettering by isoelectronic doping of p-GaAs and n-GaAs grown by molecular beam epitaxy

The effects of isoelectronic In and Sb doping on the hole traps in Be-doped p-GaAs and electron traps in Si-doped n-GaAs (100) grown by molecular beam epitaxy (MBE) have been investigated. The dominant hole traps in our Be doped layers are at about E_v+0.56 eV (H4) and may be the HL8 trap (0.52-0.54 eV) reported previously and at E_v+0.29 eV (H2). The concentrations of H4 and H2 are reduced by three orders of magnitude (from 10¹⁵ cm^-3 for H4, 10¹⁴ cm^-3 for H2) by increasing the growth temperature from 500 to 600°C. Photocapacitance measurements support the view that this trap is As⁺⁺_Ga and not a trap associated with Fe_Ga. Additions of 0.2% to 2% In or Sb for growths at 500 or 550°C have no effect on the concentration of this anti-site defect trap but cause a considerable reduction of the trap at 0.29 eV (H2). The two dominant electron traps M3 (E_c-0.33 eV) and M6 (E_c-0.62 eV) in our n-GaAs layers are drastically reduced in concentration by up to three orders of magnitude by introducing 0.2-1 at % In or Sb and increasing growth temperature from 500 to 600°C. In and Sb appear to have rather similar effects in trap gettering the concentration of the M3, M6 and H2. This suggests that these traps are in some way related to (V_AsV_Ga) complexes or (V_AsXV_Ga) complexes.