Physics of Nonlinear Transport in Semiconductors

The area of high field transport in semiconductors has been of interest since the early studies of dielectric breakdown in various materials. It really emerged as a sub-discipline of semiconductor physics in the early 1960's, following the discovery of substantial deviations from Ohm's law at high electric fields. Since that time, it has become a major area of importance in solid state electronics as semiconductor devices have operated at higher frequencies and higher powers. It has become apparent since the Modena Conference on Hot Electrons in 1973, that the area of hot electrons has ex tended weIl beyond the concept of semi-classical electrons (or holes) in homogeneous semiconductor materials. This was exemplified by the broad range of papers presented at the International Conference on Hot Electrons in Semiconductors, held in Denton, Texas, in 1977. Hot electron physics has progressed from a limited phenomeno logical science to a full-fledged experimental and precision theo retical science. The conceptual base and subsequent applications have been widened and underpinned by the development of ab initio nonlinear quantum transport theory which complements and identifies the limitations of the traditional semi-classical Boltzmann-Bloch picture. Such diverse areas as large polarons, pico-second laser excitation, quantum magneto-transport, sub-three dimensional systems, and of course device dynamics all have been shown to be strongly interactive with more classical hot electron pictures.