Investigation of the high-frequency performance of AlGaAs/GaAs HBTs down to 20 K

The temperature dependence of N-p-n AlGaAs/GaAs heterojunction bipolar transistors (HBTs) has been extensively investigated in terms of an equivalent circuit model extracted from S-parameter measurements. The measurements were performed using an on-wafer measurement setup in the frequency and temperature ranges from 45 MHz up to 50 GHz and from 300 K down to 20 K, respectively. Moreover, the temperature dependence of the emitter-base ideality factor was found to play a key role for device performance.