High-gain, low-leakage GaAs pseudo-HBT's for operation in reduced temperature environments

GaAs pseudo-heterojunction bipolar transistors (HBTs) that make use of the difference in effective bandgap narrowing in n- and p-type GaAs have been fabricated and characterized. A current gain enhancement by a factor greater than 20 is observed as the transistors are cooled to 35 K. Current gains of over 100 at a current density of 2.5*10/sup 3/ A/cm/sup 2/ were observed in transistors with a base doping 10 times the emitter doping. Tunneling currents, which previously dominated the low-temperature base current, were eliminated by the use of a spacer layer between the base and the emitter.<
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