Reactive ion etch-induced effects on the near-band-edge luminescence in GaN

GaN grown on c-plane sapphire substrates has been reactive ion etched successfully in a SF6 plasma with an etch rate of 29 nm/min. The etch rate does not change with substrate temperatures between 10 and 50 degrees C. Optical transitions have not been destroyed after etching, instead, two additional lower energy transitions appear close to the band-edge luminescence. The two additional transitions are related to defect states that bind excitons. The defect-bound states exhibit different behavior compared to the free excitonic states in that their normalized intensities decrease more rapidly as temperature increases, the peaks exist only up to 80 K, and their line energies show no temperature dependence. (C) 1999 American Institute of Physics. [S0003-6951(99)04121-2].