GaN grown on c-plane sapphire substrates has been reactive ion etched succe
ssfully 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 t
wo additional transitions are related to defect states that bind excitons.
The defect-bound states exhibit different behavior compared to the free exc
itonic states in that their normalized intensities decrease more rapidly as
temperature increases, the peaks exist only up to 80 K, and their line ene
rgies show no temperature dependence. (C) 1999 American Institute of Physic
s. [S0003-6951(99)04121-2].