CHARACTERIZATIONS OF LOW-FREQUENCY NOISE IN LASER-DEBONDED HVPE-GROWN GaN THIN FILMS

Abstract

Low-frequency excess noise was measured on laser-debonded HVPE-grown GaN films. While the Schottky MSM devices, fabricated on 5 μm-thick films, demonstrated reduction in the noise level, the ohmic MSM devices showed significant increase in the low-frequency noise. To account for the data we conducted two-dimensional simulation of the temperature of the GaN layer as a function of time and distance from the GaN/sapphire interface. The simulation results show that the temperature at the GaN/sapphire interface may rise up to 1400 K, whereas the maximum temperature at the GaN surface was about 400 K at the. Based on the experimental data and the simulation results, it is postulated that the illumination of the GaN sample by high-power excimer laser led to the decomposition of GaN at the GaN/sapphire interface resulting in the generation of localized states at the interface. The same process may have led to some thermal annealing effect at the GaN surface. To provide experimental proof of the hypothesis, detailed low-frequency noise measurement on ohmic MSM devices fabricated on 20 μm-thick GaN films were performed. The results indicate similar noise level for both the debonded and the control devices.