Channel temperature model for microwave AlGaN/GaN power HEMTs on SiC and sapphire

A key parameter in the design trade-offs made during AlGaN/GaN HEMTs development for microwave amplifiers is the channel temperature. An accurate determination can generally only be found using detailed software; however, a quick estimate is always helpful, as it speeds up the design cycle. This paper gives a simple technique to estimate the channel temperature of a generic AlGaN/GaN HEMT on SiC or sapphire, while incorporating the temperature dependence of the thermal conductivity. The procedure is validated by comparing its predictions with the experimentally measured temperatures in microwave devices presented in three recently published articles. The model predicts the temperature to within 5 to 10 percent of the true average channel temperature.