High temperature characterization of GaN-based photodetectors

In this work we report on the high temperature characterization of two different interdigitated metal-semiconductor-metal (MSM) GaN-based photodetectors. The active material of the two MSM devices consists of bulk GaN grown by metal organic chemical vapor deposition (MOCVD), and of an AlGaN/GaN heterostructure grown by molecular beam epitaxy/magnetron sputtering epitaxy (MBE/MSE) system. Some of the trapping mechanisms which are at the origin of the persistent photocurrent (PPC) effects in GaN-based devices have been studied. The analysis of the decay time as a function of the temperature shows that in both devices the GaN excitonic resonances provide the most important contribution to the PPC on the millisecond time scale at low temperature. The densities of the trap centers involved in the PPC were obtained in both samples by measuring the photocurrent as a function of optical power sweeped in the upward and downward direction.