Photoenhanced wet oxidation of gallium nitride

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