Consequences of negative differential electron mobility in insulated   gate field effect transistors
  We study the consequences of negative differential electron mobility in insulated gate field effect transistors (FETS) using the field model. We show that, in contrast to the case of the monotonic velocity saturation model, the field distributions in a short-channel FET may be described by the gradual channel approximation even for high drain-to-source voltages. The current-voltage dependence of the short-channel FET should have a branch with a negative slope. The FET exhibits a negative differential resistance and may show convective or absolute instability, depending on the applied voltages. The fluctuation growth is governed by the diffusion law with a negative effective diffusion coefficient. 
A.S.Furman