Influence of polarities on optical properties of Mg-doped GaN films grown on GaN free-standing substrates by MOCVD

Time-resolved photoluminescence measurements were performed to investigate the minority carrier recombination mechanism of p-GaN films grown on c-plane, m-plane and (10–11)-plane GaN freestanding substrates by MOCVD. The fast and slow decay lifetimes of the three samples were fitted by the bi-exponential function, in which the slow decay lifetime of the m-plane Mg-doped GaN reached a record long value of 493.7 ps? The effects of stress-induced non-radiative recombination centers and edge dislocations on the slow decay lifetime were ruled out using Raman and XRD. The reason for the longer slow decay lifetime of the m-plane sample is the reduction of the non-radiative recombination centers due to the decrease of the VGa concentration, ensuring by the magnitude of the IYL/INBE ratio in the PL spectra. The low-temperature PL spectra of the m-plane sample were investigated. According to Haynes' rule, the position of acceptor level was calibrated through combining with the position of the bound excitons at 5 K.