Influence of neutron irradiation on the deep levels in GaN

The influence of neutron irradiation on the deep levels in GaN epilayer is studied. Thermal stimulated current (TSC) and low temperature photoluminescence (PL) techniques are used to determine the position of deep levels. Four traps are found in irradiated GaN and five traps in unirradiated sample by resolving TSC spectrum. The activation energy (E_t), capture cross section (S_t), and concentration (N_t) of the traps are calculated. The possible origins of the traps are proposed. PL measurement shows that the yellow luminescence (YL) band disappears in as-irradiated GaN, and the center of blue luminescence (BL) band moves to ~3.03 eV (~2.88 eV in unirradiated sample). After annealed at 900°C, the BL band disappears too. The possible reason is discussed.