Photoluminescence of V-doped GaN thin films grown by MOVPE technique

This work reports the photoluminescence (PL) study of vanadium-doped GaN (GaN: V) in the 9-300 K range. Samples have been successfully prepared on sapphire substrates by metalorganic vapour phase epitaxy technique (MOVPE). At room temperature (RT) the PL spectra of GaN: V are dominated by a blue band (BB) in the 2.6 eV range. This BB emission is very strong and its intensity increases with increasing V doping level. We also observed that the peak position of the blue luminescence shifted at lower energy with decreasing excitation density. Upon V-doping, the yellow luminescence band shows a drastic reduction in integrated intensity. This observation is explained by a reaction involving V and gallium vacancy (_√Ga). PL spectra at low temperature exhibited a series of peaks. The donor-acceptor (D-A) pair emission peak at 3.27 eV was strongly pronounced, as the temperature was decreased. On the other hand, the intensity of the BB emission decreased. This BB emission is due to a radiative transition from a shallow donor with a depth of 29 meV to a deep acceptor with a depth of 832 meV.