An epitaxial emitter-cap SiGe-base bipolar technology optimized for liquid-nitrogen temperature operation
- 1 November 1994
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Electron Device Letters
- Vol. 15 (11) , 472-474
- https://doi.org/10.1109/55.334671
Abstract
We give the first demonstration that a properly designed silicon bipolar technology can achieve faster unloaded circuit speed at liquid-nitrogen temperature than at room temperature. Transistors were fabricated using a reduced-temperature process employing an in situ arsenic-doped polysilicon emitter contact, a lightly phosphorus-doped epitaxial emitter-cap layer, and a graded SiGe base. At 84 K, transistors have a current gain of 500, with a cutoff frequency of 61 GHz, and a maximum oscillation frequency of 50 GHz. ECL circuits switch at a record 21.9 ps at 84 K, 3.5-ps faster than at room temperature. Circuits which were optimized for low-power operation achieve a minimum power-delay product of 61 fJ (41.3 ps at 1.47 mW), nearly a factor of two smaller than the best achieved to date at 84 K. The unprecedented performance of these transistors suggests that SiGe-base bipolar technology is a promising candidate for cryogenic applications requiring the fastest possible devices together with the processing maturity and integration level achievable with silicon fabrication.Keywords
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