Effect of substrates on lasing properties of GaN transferable membranes

Abstract

Transferable membranes were separated from the GaN epitaxial sheet with lift-off (LLO) technology. After the LLO process, the GaN membrane was removed onto various substrates, and then we can create different interfacial conditions, such as GaN attached with Si and GaN attached to Au. The substrate dependent photoluminescence (PL) properties of GaN membranes are studied by PL and time-resolution photoluminescence (TRPL) measurements in situ. Lasing oscillations are observed in the GaN membranes. The lasing features – which include the lasing spectra, Q factor, laser threshold, mode number, carrier dynamics and resonance mechanism – are systematically analyzed. We obtain, for GaN on a Si substrate, two series of ultraviolet lasing emissions with Fabry-Pérot (F–P) mode at the same excitation position. Furthermore, lasing of the GaN membranes can be altered by Au film at the back end of it via the phenomenon of lasing mode merger and red shift. Comparing with the Si substrate, Au film on the back can balance the lasing oscillations through decreasing the threshold value, unifying the resonant modes, and increasing the carrier combination rate. This research provides a feasible method for the realization of flexible membrane lasers.