Off-state breakdown in power pHEMTs: the impact of the source

Summary form only given. Conventional wisdom suggests that in pseudomorphic high electron mobility transistors (pHEMTs), the field between the drain and the gate determines off-state breakdown, and that the drain to gate voltage therefore sets the breakdown voltage of the device. Thus, the two terminal breakdown voltage is a widely used figure of merit, and most models for breakdown focus on the depletion region in the gate-drain gap, while altogether ignoring the source. We present new measurements and simulations that demonstrate that for power pHEMTs, the electrostatic interaction of the source seriously degrades the device´s gate-drain breakdown, and must be taken into consideration in device design. As a vehicle for this study we have used a state-of-the-art L/sub G/=0.25 /spl mu/m double heterostructure pHEMT with excellent power performance (P/sub 0/= 1W, Gain= 11 dB, and PAE=60% at 10 GHz for W/sub G/=1200 /spl mu/m) and high breakdown voltage (BV/sub DG/=21 V at I/sub D/=1 mA/mm).