Temperature dependence of electron saturation velocity in GaAs measured in InGaP/GaAs HBT using DC and AC approaches

Temperature dependence of electron effective saturation velocity in GaAs is determined from dc and RF characteristics of InGaP/GaAs heterojunction bipolar transistor (HBT) under different substrate temperatures (from −40 °C to 200 °C). Two approaches were utilized to extract the electron effective saturation velocity in this work. The first approach is to evaluate Kirk effect both in dc current gain and cutoff frequency roll-off. The second approach is to analyze device's cutoff frequency with consideration of temperature effects in collector transit time. The deduced electron effective saturation velocity from two approaches demonstrated the similar temperature dependence. The extracted values of electron effective saturation velocity from considering collector transit time for temperatures of 200, 25, and −40 °C are about 6.43 × 106, 1.29 × 107, and 1.47 × 107 cm/sec, respectively.