Si/a-Si:H heterojunction microwave bipolar transistors with cut-off frequencies f/sub t/ above 5 GHz

The fabrication of a silicon heterojunction microwave bipolar transistor with an n/sup +/ a-Si:H emitter is discussed, and experimental results are given. The device provides a base sheet resistance of 2 k Omega / Square Operator a base width 0.1 mu m, a maximum current gain of 21 (V/sub CE/=6 V, I/sub c/=15 mA), and an emitter Gummel number G/sub E/ of about 1.4*10/sup 14/ Scm/sup -4/. From the measured S parameters, a cutoff frequency f/sub t/ of 5.5 GHz and maximum oscillating frequency f/sub max/ of 7.5 GHz at V/sub CE/=10 V, I/sub c/=10 mA are obtained.<>