Effective sulfur passivation of an n-type GaN surface by an alcohol-based sulfide solution

The sulfur passivation of an n-GaN surface was investigated by employing an aqueous (NH₄)₂S solution and (NH₄)₂S+t-C₄H₉OH solution. Photoluminescence and Auger electron spectroscopy revealed that treatment with (NH₄)₂S+t-C₄H₉OH results in a more effective passivation of the n-GaN surface than that with (NH₄)₂S due to a higher chemical reactivity of sulfur species in the former solution. The (NH₄)₂S+t-C₄H₉OH-treated sample shows a stronger photoluminescence intensity by a factor of 2.5 with respect to an untreated sample. In addition, improved Ohmic characteristics of the sample are evident from current-voltage measurements. This result can be attributed to the effective removal of an insulating layer on the n-GaN surface.