Temperature-dependent Kelvin probe studies on GaN from 80 to 600 K

In this work, we report on the effect of temperature on near-surface band bending and surface photovoltage (SPV) in GaN. Band bending and SPV during illumination and after switching the illumination off are calculated for n -type and p -type GaN by using a thermionic model. The temperature and temporal dependencies are compared with experimental data. We find that the thermionic model describes adequately the SPV values and its dynamics only at high temperatures. At temperatures below room temperature the observed SPV is much higher than predicted from the thermionic model, especially in the case of p -type GaN. This fact is explained by a significant shift of the quasi-Fermi level in p -type GaN under illumination.