In0.3Ga0.7As heterojunction bipolar transistor grown on GeSi substrate for high-frequency application

We report an In0.3Ga0.7As HBT device grown on a 200 mm Si wafer using GeSi as virtual starting substrate and InAlAs as the compositionally graded buffer layer from GaAs to In0.3Ga0.7As lattice constant. A DC gain, emitter-base, and base-collector ideality factors of 10, 1.43, and 1.56, respectively, are obtained for a device with an emitter area of 40 × 50 μm2. Small-signal simulation of an In0.3Ga0.7As HBT device with 2 × 8 μm2 emitter area shows that current gain cutoff frequency (fT) and maximum cut-off frequency (fMax), of 50 GHz and 220 GHz, respectively, can be achieved with base doping and layer thickness of 2 × 1018cm−3 and 30 nm, respectively.