Device scaling and application trends for over 200GHz SiGe HBTs

Abstract

We discuss issues and solutions for scaling of SiGe HBT devices through f/sub T/ = 350GHz. Trends in peak f/sub T/ current density J/sub CP/ and avalanche multiplication M-I are shown for devices with f/sub T/ ranging from 50GHz to 350GHz, and discussed in the context of device operation and reliability. The over 10/spl times/ current density increase observed across this f/sub T/ range may be managed by reducing emitter width and maintaining a low device thermal resistance. We show that the over 20/spl times/ avalanche current increase must be accompanied by a reduction in base resistance to maintain sufficiently high instability voltage. We also discuss the degradation from avalanche hot carriers and find this acceptable looking forward. From the circuit point of view, reversal in base current resulting from avalanche must be managed in the model and in the circuit design.