Current degradation in GaN HEMTs: Is self-heating responsible?

Electrical reliability of GaN HEMT system in both the on state and the off state regime is still a fundamental problem to be solved. To get an insight for the occurrence of the current collapse phenomena in GaN HEMTs, an electro-thermal particle based device simulator consisting of a Monte Carlo-Poisson solver, self consistently coupled with an energy balance solver for both acoustic and optical phonons, was developed. We observe that the incorporation of self-heating effects leads to an increase in the vertical electric field in the gate to drain extension region which can lead to large charge trapping on the surface and also the possibility of forming cracks or pits.