Tunneling, Current Gain, and Transconductance in Silicon-Germanium Heterojunction Bipolar Transistors Operating at Millikelvin Temperatures

In quantum computing, metrology, single-photon counting, and nanomechanics, weak electronic signals at extremely low temperatures need amplification. To this end, the authors build and study silicon-germanium heterojunction bipolar transistors, which offer excellent amplifier characteristics, integrability with silicon quantum electronics, low cost, and manufacturability. Their research at the junction of physics and electrical engineering is a step toward next-generation integrated circuits at the 90-nm scale for this temperature regime.