Thermal resistance of GaAs field-effect transistors

Characterization of the thermal resistance of GaAs FETs is presented. An electrical method of measuring it is first described. An anomaly in the thermal resistance discovered at high temperature is explained, Experimental findings are discussed on the theoretical background. Practical expressions are then derived for the thermal resistance in terms of device geometry and channel temperature. The expressions are verified to be accurate in comparison with our experimental results and with the measured values obtained by infrared microscopes elsewhere. They are useful not only for designing power GaAs FETs but also for optimizing the amplifier performance.