23 June 1994 Liquid-helium temperature operation of silicon-germanium heterojunction bipolar transistors
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Abstract
We present the first measurements of silicon-generated (SiGe) heterojunction bipolar transistors (HBT) in the liquid-helium temperature regime. We have measured the dc characteristics of SiGe HBTs from two different profile designs over the temperature range of 300 K - 4 K. The first SiGe HBT design was optimized for high-speed digital applications at room temperature (`i-p-i' SiGe HBT), and the second SiGe HBT design was specifically optimized for cryogenic operation (`emitter-cap' SiGe HBT). A silicon bipolar junction transfer (Si BJT) which has a doping profile similar to the i-p-i SiGe HBT is used as a control. The devices continue to exhibit transistor action down to the liquid-helium temperature regime, even in the presence of strong carrier freeze-out in the neutral base and collector regimes. In contrast to the Si BJT, the peak current gain of the optimized emitter-cap SiGe HBT rises monotonically from 100 to 300 K to nearly 2000 at 16 K, although parasitic base current leakage limits the useful operating range to collector currents above about 1.0 (mu) A. At very low-injection levels (less than 1.0 nA) below 77 K, we identify a non- diffusive transport mechanism in the collector current of both SiGe HBTs and the Si BJT which is unaccounted for in conventional device theory. Initial calculations suggest that this phenomenon has a bias and temperature dependence characteristic of a carrier tunneling process.
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John D. Cressler, John D. Cressler, Alvin J. Joseph, Alvin J. Joseph, David M. Richey, David M. Richey, James H. Comfort, James H. Comfort, David L. Harame, David L. Harame, Emmanuel F. Crabbe, Emmanuel F. Crabbe, Johannes M. C. Stork, Johannes M. C. Stork, } "Liquid-helium temperature operation of silicon-germanium heterojunction bipolar transistors", Proc. SPIE 2226, Infrared Readout Electronics II, (23 June 1994); doi: 10.1117/12.178491; https://doi.org/10.1117/12.178491
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