Influence of Channel Structure on the Subthreshold Swing of InGaAs HEMTs at Cryogenic Temperatures Down to 4 K

This work, for the first time, delves into and elucidates the underlying mechanism of subthreshold swing (SS) saturation in cryogenic InGaAs high electron mobility transistors (HEMTs). We proposed a pioneering interpretation of this phenomenon, grounded in the disorder resulting from potential fluctuations within the channel, which is linked to the variability in channel thickness. Our findings reveal that potential fluctuations, instigated by channel thickness variability, vary depending on the channel structure, thereby influencing the degree of disorder and SS saturation level at cryogenic temperature. This study highlights the critical need for a comprehensive understanding of the SS saturation phenomena at cryogenic temperature that govern the performance of InGaAs HEMTs for cryogenic applications. It thereby sets the stage for advancements in device design and operational optimization in ultra-steep slope cryogenic InGaAs HEMTs at cryogenic temperature.