Defect and temperature dependence of tunneling in InAs/GaSb heterojunctions

Abstract

We assess the origin of the reported temperature dependence of subthreshold slope in many published tunnel field effect transistors (TFETs) by examining the temperature dependence of the intrinsic tunneling at InAs/GaSb interfaces in the absence of three-terminal parasitics. We compare the temperature dependence of peak current, excess current, and conductance slope for interfaces with and without heavy interface defect concentrations. We identify that the tunnel and excess currents depend on temperature and defect density but that the conductance slope, a two-terminal analog to subthreshold slope, depends only on defect density and not temperature, contrasting sharply with the heavy temperature dependence seen in TFETs in literature. We propose that TFETs based on this and similar materials systems are dominated by parasitic effects such as tunneling into oxide trap states, or other parasitics that are not intrinsic to the heterojunction itself, and that in the absence of these effects, the true steepness from band-to-band tunneling is limited by defects and inhomogeneity at the interface.