Optical Spectroscopy As A Tool In Hot-Electron Studies

Abstract

Abstract The non-linear electrical conductivity of a semiconductor under the application of an electric field has been a subject of interest since the early days of semiconductor physics (Conwell 1967). At low fields, Ohm's law is obeyed and the resistance and hence the mobility of the electrons or holes remains constant. With increasing electric field, the mobility is no longer constant but begins to decrease. In III-V semiconductors, on which we concentrate in this chapter, this non-ohmic behaviour at intermediate fields can be attributed primarily to heating of the carriers by the applied electric field. Under steady-state bias, the carrier distribution function changes (i.e. the carrier temperature increases) until the rate of input of energy from the field to the carriers is balanced by the rate of loss of energy from the carriers to the lattice. Therefore, investigation of the non-ohmic transport behaviour provides information about how carriers interact with the lattice through various carrier-phonon scattering processes. At larger applied electric fields, other interesting effects such as negative differential resistance, impact ionization and dielectric breakdown occur, but we will not be concerned with these effects in this chapter.