A High-Gain AlGaAs/GaAs Heterojunction Bipolar Transistor Grown on Silicon Substrate

High gain AlGaAs/GaAs heterojunction bipolar transistors (HBTs) grown on silicon substrate have been fabricated. These HBTs-on-Si incorporate depleted AlGaAs passivation ledge to reduce extrinsic base surface recombination current and base quasi-electric field to reduce base bulk recombination current. Measured current gain of 100 is obtained for devices with an emitter area of 4×10 µm². To our knowledge, this is the highest current gain reported for AlGaAs/GaAs HBTs grown on Si substrates. The dominant base current components is determined. The leakage currents of the base-collector junctions are also examined, and are compared to similar devices grown on GaAs substrate. Implications of these observed junction characteristics of HBTs-on-Si for power applications are discussed.