Cbc Reduction in Si-implanted Subcollector HBTs

We demonstrate the first small area emitter (1.4 × 3 μm) N-p-n AlGaAs/GaAs HBTs fabricated with Nimplanted subcollectors in a high volume manufacturing environment. The subcollector region was defined by multiple N implants of various doses and energies on a semi-insulating GaAs substrate, and the remaining HBT layers were grown by MOCVD. To evaluate the impacts of Cbc reduction, devices with varying subcollector areas were fabricated for comparison. Small signal sparameter data was measured to extract fT, fmax and Cbc. By varying the implanted subcollector area, the basecollector capacitance Cbc was reduced by almost 40% using this manufacturable process. The common emitter current gain of devices fabricated by this implant/epitaxial hybrid process is about 50 which is similar to our baseline device, indicating good material quality using this technique.