Determination of HBT thermal resistance using pulsed I-V measurements

This paper describes the determination of HBT thermal resistance using a pulsed I-V measurement system. Two measurements are used to determine the thermal resistance (R/sub TH/), an isothermal measurement of the base-emitter voltage (V/sub BE/) and emitter current (I/sub C/) using the pulsed I-V system over a range of elevated temperatures and a non-isothermal measurement of V/sub BE/ and I/sub C/ over a range of collector-emitter voltages (V/sub CE/). The results of both measurements are used to determine values of power dissipation against device temperature from which R/sub TH/ can be found. The measurement of a power HBT has been carried out and the value of R/sub TH/ has been found to vary from 79/spl deg/C/W at low power levels to 108/spl deg/C/W at high power levels. This variation is a result of the change in the thermal conductivity of GaAs and has been confirmed by comparison with a theoretical model for the variation in the thermal conductivity of GaAs.