PHOTOCONDUCTIVE DECAY IN LCVD PECVD LOW-TEMPERATURE-GROWN GAN/

Photoconductive decay in undoped GaN has been investigated at room tem perature using an ArF excimer laser as illuminative source and a boxca r integrator for detection of decay signals. GaN films were grown by c ombined laser and microwave plasma enhanced chemical vapour deposition at 550 degrees C. The respective room temperature electron concentrat ion and Hall mobility of the films were measured to be in the range 10 (15)-10(16)cm(-3) and up to 200cm(2)/Vs. Two time constants, 0.8 and 6 mu s, are distinguishable in typical photoconductive decay curves and are associated with a dominant fast recombination and a weaker, slowe r process via an unidentified defect state respectively. Near-band pho toluminescence dominates the emission spectrum with little contributio n from the sub-bandgap process often found in the presence of high-den sity defects. (C) 1997 Elsevier Science Ltd.