Electron runaway and negative differential mobility in two-dimensional electron gas in elementary semiconductors

We show that two-dimensional electron gas in silicon or germanium should exhibit a negative differential mobility. This effect is caused by the electron runaway since, in contrast to the three-dimensional case, such runaway takes place even for deformation optical polar scattering. As a consequence of the electron runaway, hot electron scatter into the valleys with a larger density of states, which leads to a negative differential mobility.