Valley-dependent quasi-ballistic electron transport in FETs based on multi-valley semiconductors

We study quasi-ballistic transport in field effect transistors (FETs) with the conductive channels containing several groups of the carriers. These groups are considered independent in the sense of the absence of inter-group exchange, but their dynamics is strongly coupled through collective electrostatic potential. In particular, for FETs based on multi-valley semiconductors, we show that the quasi-ballistic transport is significantly valley-dependent and the currents induce valley polarization with peculiar spatial distributions of the carriers for every valley. In turn, the valley polarization affects the currents and voltage distributions in the FET channels. The importance of the valley-dependent effects is illustrated for different examples of Si-based FETs and AlAs-FETs. We suggest that the disclosed valley polarization by the current in FETs can be also used in the emerging discipline of valleytronics.