The influence of Si on the properties of MOVPE grown GaN thin films: Optical and EPR study

Abstract

Metal Organic Vapour Phase epitaxy (MOVPE) grown GaN layers doped with Si were studied by means of radio-, photo- and thermally stimulated luminescence, scintillation decay kinetics, as well as electron paramagnetic resonance. Two luminescence bands were observed: the narrow and fast peaking at about 3.45 eV (ascribed to excitons) and the broad and slow one having maximum at about 2.2 eV (produced by the defect – a carbon occupying nitrogen site). The decay time and the intensity of exciton and defect-related emission exhibit dependence on the doping level of Si. Both bands are getting faster upon the increased Si content. Moreover, the presence of Si influences drastically the charge trapping processes as well – the changes in the intensity of the glow peaks within the 100–300 K temperature range were observed. Besides, the new glow peaks appear and are getting stronger in the 300–450 K region upon Si doping. Interestingly, the effect of Si on the conductivity properties of the GaN samples was observed by means of electron paramagnetic resonance.