Temperature dependence of GaAs metal-semiconductor field effect transistor threshold voltage

We have investigated the temperature dependence of threshold voltage (Vth) of n‐channel GaAs metal–semiconductor field effect transistors with different gate materials and structures. It is found that Vth increases by 0.3–0.4 V as temperature decreases from 350 to 80 K.
The Vth versus temperature relationship is approximately linear. The amount of Vth shift is independent of channel length from 0.8 to 3 μm and it does not strongly depend on the gate material used. Similar Vth increases are observed for different channel doping methods, such as ion implantation and molecular‐beam epitaxy growth.
Different GaAs substrates only show a small effect on the Vth temperature dependence. Calculations show that Fermi‐level shift and energy‐gap expansion with decreasing temperature account for only a fraction of the observed change in Vth.
Our measurements indicate that the extra Vth shift is not mainly due to deep‐level traps within the channel. Results from C–V measurements on metal/GaAs diodes suggest that build‐in voltage changes with temperature are principally responsible for the Vth shift.