Patterned n+ implant into InP substrate for HBT subcollector

We demonstrate molecular-beam epitaxy (MBE)-grown heterojunction bipolar transistors (HBTs) on InP substrates with a patterned implant n+ subcollector below the epitaxial layers. Device layers grown on implanted/annealed substrates were of similar quality to those on virgin InP. Maximum f/sub t/ and f/sub max/ of 240 and 310 GHz were obtained. We present the process flow, details of the ion implantation, layer characterization, and device results.