Performance degradation of GaN field-effect transistors due to thermal boundary resistance at GaN/substrate interface

The authors investigate the effect of the thermal boundary resistance between the GaN layer and the substrate on the current-voltage characteristics of GaN MESFETs. Using material specific models for carrier drift-diffusion and thermal conductivity the authors determine the dependence of the breakdown voltage on thermal boundary resistance. The mechanism of the thermal breakdown in GaN transistors is also discussed. Obtained results can be used for structure optimisation of GaN-based transistors.