Temperature effects on DC and small signal RF performance of AlGaAs/GaAs HEMTs

We here report on the DC and microwave performance of HEMTs tested on wafer under different temperature conditions. The relevant experimental data show that the most important electrical parameters, such as the output current, the threshold voltage, the transconductance and the forward transmission coefficient, are sensibly affected by thermal phenomena. We focused our attention on the variations of the above parameters with the temperature because such a detailed knowledge is essential to establish the optimum bias point for a given application. Furthermore, we analyze the influence of the DC quiescent point degradations, due to thermal phenomena, on the small signal equivalent circuit. Since the thermal behavior of the circuit model is a function of the bias, we examine the behavior of the circuit elements vs. temperature over a wide range of bias conditions.