Effect of photoelectrochemical oxidation on properties of GaN epilayers grown by molecular beam epitaxy

GaN epilayers grown by molecular beam epitaxy were photoelectrochemically ( PEC) oxidized in an aqueous KOH solution. The oxidation effect was investig ated by defect-related photoconductivity and photoluminescence. The PEC tre ated GaN show decreased extrinsic photoresponse and concentration of deep l evel states in comparison with the as-grown sample. The PEC process also re sults in enhanced donor-bound exciton photoluminescence at 3.47 eV and rest rained 3.4 eV band. No strain is detected in the PEC oxidized GaN. The 3.4 eV band is related to structural defects instead of oxygen impurities. Rath er, the defects can be passivated by the PEC oxidation. (C) 2001 American I nstitute of Physics.