Temperature dependent dynamic on-state resistance in GaN-on-Si based normally-off HFETs

Abstract

Enhancement-mode GaN-on-Si HFETs for power switching application are investigated under fast switching and elevated ambient temperatures conditions. The switching characteristics are used to evaluate the dynamic on-state resistance at temperatures up to 175°C, while switching drain voltage up to 400V. The devices show a low increase of <25% in dynamic resistance when increasing the ambient temperature up to 125°C. However, differing from expectations, above this temperature a rapid increase of on-resistance up to 85% occurs. Such anomaly indicates the existence of thermally activated trapping processes. Trapping transients taken over a large temperature range and a wide range of off-state stressing time show that in parallel to the buffer trapping, with activation energy of 0.80±0.02eV, an additional de-trapping process with activation energy of 0.42±0.05eV occurs through increased leakage current over the temperature.