Millimeter-wave AlGaAs/GaAs p-n-p HBT

The total emitter-to-collector delay for a p-n-p AlGaAs/GaAs heterojunction bipolar transistor (HBT) has been reduced to 5.7 ps by extending the cutoff frequency for these devices to the millimeter-wave range. A total charging delay of 1.2 ps was obtained by a lightly doped emitter and by reducing the collector resistance. Low transit delays totaling 4.5 ps were achieved with a thin (440 AA) uniformly doped base and a thin (2800 AA) collector. The reduction in these delays permitted a non-self-aligned (1- mu m emitter mesa/base contact separation) device with two emitters (2.6*10 mu m/sup 2/ each) and a single base contact to exhibit an f/sub t/ of 28 GHz.<
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