Noise and electrical characteristics below 10 K of small CHFET circuits and discrete devices

摘要

This paper discusses the latest results of a continuing study of the properties of the complementary heterojunction field-effect transistor (CHFET) at 4 K. The electrical characteristics, including the gate leakage current and the subthreshold transconductance, and the input-referred noise voltage for a new lot of discrete CHFETs is presented and discussed. It is shown that the inclusion of a sidewall spacer on the gate substantially reduced the gate leakage current, as compared to a previous lot without the sidewall spacer. The input-referred noise is approximately the same order of magnitude as previous devices, on the order of 1 $mu@V/$ROOT@Hz at 10 Hz for subthreshold operation. The noise is relatively unaffected by changes in the bias current and drain voltage, but decreases with increasing device size, and is increased by the inclusion of dopants in the channel region. Several simple multiplexer circuits using CHFETs are presented, and the open-loop transfer curve of a multiplexed single gain stage operational amplifier at 4 K is shown.