In-situ Monitoring of Surface Modification of GaN Films Exposed to Inductively-Coupled Plasmas

This paper reports in-situ monitoring of surface modification of plasma-treated GaN films based on photoluminescence (PL) technique. Irradiation of 313 nm ultraviolet (UV) light induced the photoluminescence of the GaN film, which typically consists of ~365 nm luminescence caused by transition between near band edges (NBE) andbroad yellow luminescence (YL) for an approximate wavelength range of 480-700 nm corresponding to defect-states-related transition before plasma exposure. However, after turning on discharges, a broad blue luminescence (BL) of 400-480 nm was also observed, and the BL intensity significantly increased, whereas the NBE and the YL decreased after the plasma exposure. The plasma-induced significant nitrogen deficiency near top surface will cause the decreases in both the NBE and the YL as non-emissive defects, and diffusion of the defects in the depth direction will attribute to the appearance of the BL. These results suggested that the PL measurements is useful for in-situ surface monitoring of plasma-treated GaN films. This work is partly supported by the 2nd stage Knowledge Cluster Initiative and Grant-in-Aid for Scientific Research (C) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.