A distinctive bound exciton line induced by electron-beam irradiation and subsequent annealing of an unintentionally doped GaN layer

An undefined bound exciton line (UDX) with a photon energy 0.6 meV lower than the Si-donor bound exciton line was observed by photoluminescence in gallium nitride (GaN) layers annealed at 1100 °C after electron beam (EB) irradiation at an energy of 137–2000 keV. The UDX was not observed in samples not subjected to EB irradiation or annealing but was found in a sample annealed after EB irradiation at an energy of 137 keV, where only nitrogen atoms are displaced in GaN. The origin of the UDX was presumably formed by a thermal reaction of defects containing nitrogen-displacement-related defects.