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Shaahin G Shirazi

Why the effect of temperature is different at on and off-state current?

For V(drain)=0.1V or 0.4V and V(gate)=0V, by increasing the temperature (300ºk, 400ºk, 500ºk) the current (off-state current) increases. Such behavior can be seen for V(drain)=0.4V and V(gate)=1V (on-state current). But for V(drain)=0.1V and V(gate)=1V the current decreases with temperature.

At low gate bias it’s common. By increasing the ambient temperature thermal leakage current over top of the potential barrier increases.(caries obtain enough energy for escaping from region under Fermi level of the source to top of the potential barrier).But for high gate field what is the reason of varying the current by temperature?

Why the effect of temperature on current is different for different bias conditions? Does it arise from scattering process? What scattering?

The structure was selected coaxial and all parameters for device and simulator setting were kept as default.

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    SungGeun Kim

    At a high gate bias and a high drain bias, if you increase temperature, the Fermi function spread more in the contact and hence the region where the current is flowing is broadened. Because current=int f(E)*T(E) where f is the Fermi function and T is the transmission, assuming T(E) remains the same as we increase temperature, f(E) spread out and higher subbands starts to carry current and more current can possibly flow because at higher energy more subbands carry the current and T(E) is larger at high energy.

    However, when you reduce the drain bias, the Fermi function in the drain side is also important. The current flowing from source to drain is starting to balance with the current from drain to source. And only the tail of the fermi function at the source side is carrying the current, so as you increase temperature, the tail in the fermi function in the source side becomes smaller and the current decrease.

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