The transient exclusion effect in intrinsic semiconductors

Abstract

The process of formation and relaxation of charge-carrier exclusion in a structure with an h–l-junction has been studied both theoretically and experimentally. It is shown, for the first time, that temporal dependencies of the most important process characteristics, such as the exclusion length, the extent of integral charge-carrier depletion in the base, and the current establishment, may be expressed by simple analytical formulae. The modelling experiment has been carried out using Ge crystals with intrinsic conductivity (T ≥ 300 K). In order to ‘visualize’ the spatial distribution of the charge carriers, the transmission beyond the edge of fundamental absorption and non-equilibrium thermal emission of the structure base in the spectral range 8–12 μm have been investigated. It is shown that thermal generation of charge carriers by the ohmic contact and base surface plays a key role in the process of exclusion relaxation. The difference between process duration in the cases of establishment of a steady-state current and spatial-charge-carrier distribution is explained by the formation of a high electric field domain.