Low-electron-energy cathodoluminescence study of polishing and etching effects on the optical properties of bulk single-crystal gallium nitride

摘要

Low electron energy cathodoluminescence (LEECL) was used to examine polishing-induced damage in a bulk high-pressure grown GaN single-crystal platelet.The Ga-polarity face of the platelet was mechanically polished;chemically-assisted ion-beam etching (CAIBE) to a depth of 200 nm was performed on a portion of this face.Low-temperature (15 K) CL spectra of the polished-only and polished+CAIBE regions of the Ga-face were taken at 2.8 kV,5.4kV,and 10.6kV (corresponding to average electron penetration depths of 19 nm,56nm,and 170nm).The low-temperature CL spectrum of the unpolished,N-polarity face was taken at 10.6 kV.In the near-band-edge region,all the CL spectra from the Ga-polarity face show a narrow peak near 3.47 eV,ascribed to donor-bound exciton recombination,and several overlapping peaks at lower energy (3.1 eV to 3.4 eV),ascribed to defect-related levels or to donor-acceptor pair recombination.