Defects related to N-sublattice damage in electron irradiated GaN

Abstract

Defects related to the N-sublattice of GaN are studied with electron irradiation. Selective damage of the N-sublattice is achieved by irradiating the samples with 0.42 MeV electrons. A new shallow donor B 1 with binding energy of 24.9±0.4 meV was found after irradiation with ground state bound exciton emission at 3.4732 eV. Among the possible defects, the nitrogen vacancy (V N) is the most likely candidate for the new donor B 1. In addition, an interesting change in the excitonic luminescence of the irradiated sample is observed under focused 267 nm laser beam illumination at cryogenic temperatures. The intensities of O NX A and Si GaX A, the total band edge luminescence intensity, and the luminescence decay lifetime of free and bound excitons all increase with laser exposure time, and the relative intensity of the B 1-bound exciton emission decreases. This effect is not observed with below bandgap illumination. We propose that this reflects the light-induced dissociation of non-radiative defect complexes of O N and Si Ga with N i, subsequently the migration of N i and then at least partial annihilation of N i with V N. The new donor B 1-bound exciton emission and the light-induced instability start to disappear upon annealing around 300 °C, indicating the thermal dissociation of donor–nitrogen complexes and annihilation of the irradiation-induced vacancy- and interstitial-type defects.