Planar device isolation for InP based DHBTs

Device isolation of InP based HBTs in the mesa technology, is done by etching down to the substrate; this process suffers from lack of planarity and does not lend itself well to high levels of integration. We report on two techniques for planar isolation of InP based HBTs using selective implantation. The first method involves Fe implantation to isolate the InP collector-subcollector layers. In the second approach, we have utilized selective Si implantation in SI InP to form an isolated, N++ subcollector.