Dry-etch fabrication of reduced area InGaAs/InP DHBT devices for high speed circuit applications

We have fabricated reduced area InGaAs/lnP DHBTs for high speed circuit app lications. To produce the small dimensions required, a process involving bo th wet chemical and ECR plasma etchingwas developed. Optical emission spect ros-copy 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 x 3 mu m(2) emitter size devices with a 500 Angstrom base.