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

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Abstract
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.

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