Si/Si/sub 1-x/Gex heterojunction bipolar transistors with high breakdown voltage

Heterojunction bipolar transistors are desirable for microwave applications because a low base resistance can be achieved yielding high maximum frequency of oscillation. Here we report Si/Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors with high breakdown voltages and excellent small-signal microwave characteristics. The transistors structures were grown by molecular beam epitaxy and fabricated by a double-mesa process. Measured f/sub T/ and f/sub max/ were 10 and 22 GHz, respectively, for transistors with BV/sub CBO/ of 40 V.>