High-field effects in sub-micron devices

The confinement of an electron to a quantum well (QW) degrades its mobility as a result of modification in the energy spectrum from an analog to a digital one. Diffusive and drift electron transport in a sub-micron device subjected to a high electric field is evaluated using a steady-state asymmetric distribution function. The Einstein ratio of the diffusion coefficient to mobility is considerably enhanced due to mobility degradation in a high electric field and more so under ac conditions. An alternative description of this enhancement in terms of hot electron temperature, both under ac and dc conditions, is also given.