Boundary-condition-induced current overshoot in short GaAs samples

The effect of boundary conditions on current overshoot observed in transient nonstationary simulations of electron transport in submicrometer bars of GaAs is described. Noting that the one-valley model for GaAs does not give rise to observable overshoot when the spatially independent Boltzmann transport equation (BTE) is solved, significant current overshoot is reported when the same model is used in the solution of the spatially dependent BTE with replacement boundary conditions. The spatially unidimensional, time-dependent BTE is solved for undoped GaAs samples with lengths varying between 0.2 and 1 mu m. The amount of current overshoot varies depending on the length of the sample and is seen to be as high as 10%. The phenomenon is explained using the moments of the Boltzmann equation.<
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