Analysis and Modeling of Negative Transconductance in Zero-Threshold Voltage MOSFETs at Cryogenic Temperatures

In this article, we present a comprehensive overview of the negative transconductance observed in native (or zero-threshold) MOSFETs at cryogenic temperatures. These devices exhibit negative transconductance, characterized by a drop in the drain-to-source current as the gate voltage increases below 77 K. The parameters related to mobility and threshold voltage exert an influence on the negative transconductance. Based on an in-depth analysis of these parameters on the characteristics of zero-threshold voltage devices, we present a modeling methodology that effectively incorporates the negative transconductance effect using BSIM-BULK as the core model. The model results are validated with the experimental data, demonstrating an excellent match between the two.