Strong Spatial Dependence of Electron Velocity, Density, and Intervalley Scattering in an Asymmetric Nanodevice in the Nonlinear Transport Regime

Using a 2-D ensemble Monte Carlo method, we have studied the electron transport in a self-switching device, which is a semiconductor rectifier consisting of an asymmetric nanochannel. Apart from obtaining a good agreement between the theoretical and experimental current-voltage characteristics, the focus is to study the detailed electron transport inside the nanochannel. Our simulations reveal a drastic spatial dependence of the electron velocity, density, and intervalley scatterings along the channel direction because of the strongly nonlinear transport combined with the asymmetric device geometry. We show that pronounced negative differential electron velocity actually occurs in certain regions inside the channel and changes under different bias conditions. Electron intervalley transfer is also found to depend strongly on the sign of the bias voltage as well as the spatial location in the channel. Moreover, we find that it can take a distance of up to 1 mum for the hot electrons to relax their energy after passing through the nanochannel at high biases. The implications on device operating speed and integration are discussed.