Photoenhanced wet oxidation of gallium nitride

We investigate the photo-oxidation process and the corresponding passivatio n effects on the optical properties of unintentionally doped n-type gallium nitride (GaN). When illuminated with a 253.7 nm mercury line source, oxida tion of GaN is found to take place in aqueous phosphorus acid solutions wit h pH values ranging from 3 to 4. At room temperature, the photo-oxidation p rocess is found reaction-rate limited and has a peak value of 224 nm/h at p H=3.5. Compared with the as-grown GaN layers, threefold enhancement in the photocurrent and photoluminescence response are observed on the oxidized Ga N surfaces. These results are attributed to the surface passivation effects due to the deep ultraviolet-enhanced wet oxidation on GaN. (C) 2000 Americ an Institute of Physics. [S0003-6951(00)00704-X].