The electronic recombination properties of Mg-doped GaN were investigated by using steady-state and time-resolved cathodoluminescence in the scanning electron microscope, photo-current spectroscopy and optical beam-induced current methods. The cathodoluminescence and optical beam-induced current maps reveal an inhomogeneous recombination activity in the investigated material. Deep levels giving rise to level-to-band transitions were detected by photocurrent spectroscopy. A large photocurrent quenching observed upon illumination with light of 2.65 to 2.85eV was tentatively attributed to metastable traps within the band gap. Cathodoluminescence spectra reveal the existence of emission bands centered at 85K at 3.29, 3.20, 3.15 and 3.01eV, respectively. Both time-resolved and steady-state cathodoluminescence measurements carried out under different excitation conditions indicated that the 3.15 and 3.01eV emissions were likely related to donor-acceptor pair transitions. Time-resolved cathodoluminescence measurements also reveal different recombination kinetics for these bands and suggested that deep donors were involved in the mechanism responsible for the 3.01eV emission.

Defect Assessment of Mg-Doped GaN by Beam Injection Techniques. C.Díaz-Guerra, J.Piqueras, A.Castaldini, A.Cavallini, L.Polenta: Journal of Applied Physics, 2003, 94[12], 7470-5