Optimization of silicon bipolar transistors for high current gainat low temperatures |
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Authors: | Woo J.C.S. Plummer J.D. |
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Affiliation: | Integrated Circuits Lab., Stanford Univ., CA; |
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Abstract: | Bipolar transistors designed specifically for operation at liquid-nitrogen (LN2) temperature are discussed. It is found that for high-gain LN2 bipolar transistors, the emitter concentration should be around 5×1018 cm-3. Compensating impurities in the base should be kept to minimum. Test bipolar transistors with polysilicon emitter contacts were fabricated using these criteria. The devices show very little current degradation between room temperature and 77 k. Polysilicon emitter contacts are also shown to be somewhat more effective at lower temperatures |
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