On the Low-Temperature Static and Dynamic Properties of High-Performance Silicon Bipolar Transistors

Abstract

We present a detailed investigation of the static and dynamic properties of high-performance silicon bipolar transistors in the temperature range of 400 to 77 K. Transistors are found to have near-ideal characteristics at low temperatures with as high as 80 at 77 K. Detailed calculations indicate that the conventional theory of the temperature dependence of β does not match our data. This discrepancy can be removed if we assume that a phenomenalogical thermal barrier to hole injection is present. ECL ring oscillators are functional at 85 K with no degradation in speed until about 165 K when compared to 358 K (85 °C). Calculations using a delay figure of merit indicate that fT, Rb, and Cc are the delay components most affected by low-temperature operation. The feasibility of reduced logic swing operation of bipolar circuits at low temperatures is examined. We find that successful ECL circuit operation at reduced logic swings is possible provided emitter resistance is kept small and can be used to enhance low-temperature power-delay performance. Together, these data suggest that conventionally designed high-performance bipolar devices may be suitable for the low-temperature environment. © 1989 IEEE