Si-implanted subcollector heterojunction bipolar transistors
npn AlGaAs/GaAs heterojunction bipolar transistors (HBTs) fabricated using an Si-implant to form the subcollector followed by MOCVD growth of the remaining structure are demonstrated. The common emitter current gain of large test devices is ~50 at a collector current density of 1.9 × 103 A/cm2. The base-collector and emitter-base current ideality factors are 1.08 and 1.26, respectively. Co-implantation with Se reduced the subcollector sheet resistance to 13 Ω/□. Patterning of this implanted subcollector will result in a significant reduction of extrinsic base-collector capacitance (Cbc).