Donor-hydrogen bound exciton in epitaxial GaN

An emission, named (D₂⁰,X), located at {~}3.48 eV at low temperature, in the near-band-edge spectrum of GaN, was investigated by photoluminescence (PL). This (D₂⁰,X) emission is close in energy to the well-studied neutral-donor-bound-exciton (D⁰,X) line in GaN. They are distinguished by a variety of PL measurements in this study. Excitation power and temperature-dependent studies indicate that this emission is related to a bound exciton complex. Annealing at a relatively low temperature {~}440 ^∘{}C results in a dramatic reduction of the PL intensity of this emission. A model is proposed that the exciton-binding center responsible for the (D₂⁰,X) emission consists of a (shallow) donor-hydrogen complex that is formed in the GaN epilayer during the growth. The annealing at 440 ^∘{}C results in the dissociation of this complex and thus reduces the PL intensity of the (D₂⁰,X) emission.