We have fabricated reduced area InGaAs/InP DHBTs for high speed circuit applications. To produce the small dimensions required, a process involving both wet chemical and ECR plasma etching was developed. Optical emission spectroscopy was used for end-point detection during plasma etching. With this improved process, an f t of 170 and f max of 200 GHz were achieved for 1.2 × 3 µm 2 emitter size devices with a 500 Å base.