ZnSe—Ge heterojunction transistors

Heterojunction transistors are described consisting of n ZnSe epitaxially deposited on Ge base-collector junctions. The low-frequency common-emitter current gain is analyzed in terms of the injection efficiency and base transport factor. The injection efficiency is limited by interface recombination and capture-tunneling components in the emitter current, and the transport factor by low base lifetimes resulting from lattice and thermal mismatches involved with heterojunctions. Experimentally, the gain is constant at low injection levels and varies as a fractional power of the current at higher levels. The gain improves with decreased base widths and higher fields. Increasing the emitter resistivity reduces the capture-tunneling component in the emitter current, and increases the gain. Relatively small temperature dependence is observed, with β decreasing slightly at lower temperatures.