Application of low-frequency noise measurement as a characterization tool for laser-assisted debonding of GaN-based devices

In this paper we present experimental results on the development of high-performance GaN LEDs and HEMTs by laser-assisted debonding of the sapphire substrates from the GaN active layer. Detailed discussions on the process and characterizations of the electronic, optical, structural and low-frequency noise properties are presented. In particular, low-frequency noise characterization is shown to shed light on the crystalline properties of the GaN materials before and after the debonding process and is instrumental in the optimization of the debonding process. Our results show that using the optimized laser power GaN-based LEDs and HEMTs can be detached from the sapphire substrates with little degradation in the device properties. In the case of LEDs, we have investigated the application of photo-electrochemical etching of the GaN to increase surface roughness of the flip-chip bonded device. This is shown to result in over 60% improvement in the efficacy of the LEDs.