Cbc Reduction in Si-implanted Subcollector HBTs

We demonstrate the first small area emitter (1.4 × 3 µm 2 ) N-p-n AlGaAs/GaAs HBTs fabricated with 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 s- parameter data was measured to extract fT, fmax and Cbc. By varying the implanted subcollector area, the base- collector 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.