Observation of Hot Electron and Impact Ionization in N-Polar GaN MIS-HEMTs

This letter reports on the observation of hot-electron and impact-ionization mechanisms in N-polar GaN-based MIS-HEMTs designed for high frequency (RF) operation. Thanks to the extremely low gate leakage of such devices, we were able to demonstrate-for the first time-a correlation between electroluminescence (EL) and gate current in the semi-on state. In the semi-on state, the devices show a non-monotonic, bell-shaped behavior of the EL-versus-V-GS and of the I-G-versus-V-GS characteristics, and the intensity of the EL signal is proportional to the I-G x I-D product. The results are experimental evidence for impact ionization: the related mechanisms are described in detail in the letter.