Abstract
A theoretical investigation of Si/Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors (HBTs) undertaken in an attempt to determine their speed potential is discussed. The analysis is based on a compact transistor model, and devices with self-aligned geometry, including both extrinsic and intrinsic parameters, are considered. For an emitter area of 1*5 mu m/sup 2/, an f/sub t/ of over 75 GHz and f/sub max/ of over 35 GHz were computed at a collector current density of 1*10/sup 5/ A/cm/sup 2/ and V/sub CB/ of 5 V.