Performance of new self-aligned InP/InGaAs HBT's using crystallographically defined emitter contact technology

The performance of InP/InGaAs heterojunction bipolar transistors (HBT's), fabricated using a new crystallographically defined emitter contact technology, is investigated. In this technology, a new self-alignment process has been developed based on the crystallographic wet etching characteristics of an InP dummy emitter layer according to the crystal orientation. The shape of the emitter electrode, which is determined by the crystallographically etched sidewall of the InP dummy emitter layer, is used for obtaining the desired contact spacing between the emitter mesa and the base electrode. The fabricated HBT's show good overall device performance at high frequencies with a current gain cutoff frequency f/sub T/ of 94 GHz and a maximum oscillation frequency f/sub max/ of 124 GHz. The microwave power performance of the device was also measured and characterized.