p-n-p heterojunction bipolar transistors with buried subcollectorlayers

The buried-layer technology was applied to the fabrication of high-speed p-n-p AlGaAs/GaAs heterojunction bipolar transistors (HBTs). The subcollector layer was selectively implanted prior to the epitaxial growth of the rest of the device structure thereby eliminating the need for deep mesa isolation. Devices with 2×10-μm² emitter fingers and 100-nm base thickness had common-emitter current gains of 15 and cutoff frequencies of 17 GHz