Si/SiGe heterojunction bipolar transistors with current gains up to 5000

Si-SiGe heterojunction bipolar transistors were fabricated in a process including 900 degrees C processing. The current gain beta reaches 5000 for 30- mu m-wide emitters. Surface recombination reduces beta in narrow-emitter transistors. Recombination centers, essentially in the base layer, affect beta and may degrade the DC output characteristics. The transit frequency was measured to be 12 GHz at V/sub CE/=3 V.<
>