Novel self-aligned sub-micron emitter InP/InGaAs HBT's using T-shaped emitter electrode

Abstract

A new self-aligned process for InP/InGaAs heterojunction bipolar transistors (HBTs) using a T-shaped emitter electrode has been developed. In this process, the T-shaped emitter electrode is used to allow the desired spacing between the emitter mesa and the base ohmic contact. The thickness of the emitter cap and emitter can be thinned independently of the base metal thickness. The thin emitter cap and emitter reduces the difference in characteristics due to the two emitter electrode orientations, parallel and perpendicular to orientation flat. A fabricated HBT shows a cutoff frequency (f/sub T/) of 98 GHz with a 0.9 /spl mu/m/spl times/4.7 /spl mu/m sub-micron emitter and a maximum f/sub T/ of 120 GHz with a 1.4 /spl mu/m/spl times/4.7 /spl mu/m emitter after it is embedded.