A Study of Photoelectrochemical Oxidation of GaN Epilayers by Extrinsic Photoconductivity

2001 
GaN epilayers grown on sapphire substrates by molecular-beam epitaxy were oxidized by photoelectrochemical (PEC) treatment in KOH. The effect of the oxidation on the GaN surface was investigated by extrinsic photoconductivity. The PEC-treated samples show decreased photoresponse and relaxation time compared with those of the as-grown sample. The concentration of deep states in the epilayers as determined from the light-intensity dependence of rise and decay times is reduced after PEC oxidation. The results suggest that the defective bonds at the surface are effectively saturated by oxygen coverage during PEC growth of the oxide layer. Results of temperature-dependent photoconductivity measurement reveal that shallow levels are also passivated within a short time of PEC treatment.
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