Direct experimental evidence for the role of oxygen in the luminescent properties of GaN

We present experimental evidence of electron-beam-induced diffusion of O and H in unintentionally doped n-type GaN grown on a sapphire substrate. Impurity diffusion was investigated using cathodoluminescence kinetics and imaging at 4 and 300 K and by wavelength dispersive x-ray analysis. The results illustrate the significance of electron-beam-induced electromigration in wide band gap semiconductors, confirm the roles of ${\mathrm{O}}_{\mathrm{N}}^{\mathrm{•}}$ in bound exciton, donor-acceptor pair and yellow emissions and suggest the involvement of ${\mathrm{O}}_{\mathrm{N}}^{\mathrm{•}}$ and hydrogenated gallium vacancies in the previously unexplained blue luminescence.