THERMAL-STABILITY OF GAN INVESTIGATED BY LOW-TEMPERATURE PHOTOLUMINESCENCE SPECTROSCOPY

We have studied the thermal behavior of 1-mum-thick GaN films grown by plasma-enhanced molecular beam epitaxy. Samples were annealed at elev ated temperatures in a nitrogen environment and were characterized by low-temperature photoluminescence (PL). After GaN samples were anneale d at up to 700-degrees-C, the free-exciton transition PL line intensit y improved. This PL line intensity degraded when annealing temperature s reached 900-degrees-C. After annealing at 900-degrees-C, GaN samples with inferior crystalline quality exhibited a line at 2.3 eV attribut ed to point defects and antisite defects.