Switching voltage, dynamic power dissipation and on-to-off conductance ratio of a spin field effect transistor

The metal-insulator-semiconductor (MIS) and high electron mobility transistor (HEMT) implementations of the spin field effect transistor (SpinFET) proposed by Datta and Das are considered. In both configurations, the SpinFET's switching voltage (for switching on or off) and power dissipation are found to be larger than those of the traditional MISFET or HEMT if the channel length is ≤90 nm. This is a consequence of the fact that spin orbit interaction strengths in semiconductors are too weak to impart any significant advantage to the SpinFET. The issue of non-ideal spin injection and detection at the source and drain contacts is also considered. The SpinFET's on-to-off conductance ratio rapidly degrades with decreasing spin injection/detection efficiency, dropping from infinity (for a one-dimensional channel) to as low as ∼9.5, if the spin injection/detection efficiency drops from 100% to 90%. The transconductance has a quadratic dependence on the spin injection efficiency. These analyses are valid at arbitrary temperatures.