Current-voltage and frequency response characteristics of low-noise bipolar transistors at cryogenic temperatures

Abstract

We present experimental current–voltage, frequency response, and noise characteristics of modern low-noise silicon bipolar n-p-n (SSM2212) and p-n-p (SSM2220) transistors at cryogenic temperatures. We have measured the frequency response characteristics in the frequency range from 10 Hz to 102 kHz. The obtained results show that low temperature effects in semiconductor structures affect significantly the transistors’ performance. In particular, we have observed a decrease of the collector current, a strong increase of the base current and a drop in the current gain. Also, the noise performances of transistors demonstrate the voltage noise reduction below 0.4 nV/Hz1/2@1 kHz for SSM2212 and below 0.3 nV/Hz1/2@1 kHz for SSM2220 at 77 K, but with the current noise being increased, reaching about 10 pA/Hz1/2@10 kHz. We show the possibility of using the bipolar transistors at cryogenic temperatures down to 50 K. This possibility is due to significant improvements in bipolar technology in recent years. We demonstrate the voltage gain of the common-emitter circuit is about of 30 at 48 K, indicating its suitability for use in cryogenic amplifiers.