SURFACE ACOUSTIC WAVE PROPAGATION IN GaN-ON-SAPPHIRE UNDER PULSED SUB-BAND ULTRAVIOLET ILLUMINATION

Abstract

We investigated transient amplitude and phase response of GaN -on-sapphire SAW delay-line device subjected to pulsed sub-band UV illumination. We correlated these results with photoluminescence measurements in two GaN samples with the same emission spectra but different carrier lifetime. The SAW response measurements showed that under pulse illumination the sample with shorter lifetime exhibited gradual rise in the phase and amplitude change in millisecond range. Under similar conditions, the sample with a longer lifetime responded faster. We attribute this change to the presence of defect related transitions of the photoexcited carriers and their interaction with surface acoustic waves. Our results demonstrate the possibility of characterization of compensated GaN samples by measuring the phase and amplitude variations in the SAW transmission mode under pulsed UV excitation.