Relationship between defects and optical properties in Er-doped GaN

The density of the vacancy-type defect in Er doped GaN was measured by positron annihilation spectrometry (PAS) and the correlation between the intensity of the Er-related luminescence was studied. A luminescence peak at 558 nm originating from ⁴S_3/2 to ⁴I_15/2 transition of Er³⁺ was observed in Er-doped GaN. The intensity of the luminescence increased with increasing Er concentration and showed the maximum with the Er concentration of around 4.0 at%. The PAS measurements showed that the vacancy-type defect density increased with increasing Er concentration up to 4 at%, and around 4 at% of Er, the formation of defect complex such as V_Ga-V_N was suggested. The contribution of the defect to the radiative recombination of intra-4f transition of Er is discussed.