On the use of vertical superjunction collectors for enhanced breakdown performance in SiGe HBTs

The implementation of a “superjunction” collector design in a silicon-germanium heterojunction bipolar transistor is explored for enhancing breakdown performance. The superjunction collector is formed through the placement of a series of alternating pn-junction layers in the collector-base space charge region to modify the carrier energy profile and reduce avalanche generation. An overview of the physics underlying superjunction collector operation is presented with TCAD simulations, and practical superjunction design techniques are discussed. The first measured data on a superjunction collector is also presented and shows a 57% improvement in breakdown performance.