ABSTRACT
Fluctuation phenomena in semiconductors are due to the statistical nature of different physical processes in these materials. For example, the statistical nature of the scattering of free charge carriers causes random changes in their velocities and, hence, random microscopic diffusion currents. In the theoretical examination of noise in semiconductors one may restrict oneself, in many cases, to the simplest model of a semiconductor where electron transitions occur only between two energy levels. The Langevin method is based on the assumption that fluctuations are caused by stochastic sources. Van Vliet has analysed the properties of the Langevin noise sources using the short-time solution of the Langevin equations. The momentum method has been applied to the study of fluctuation phenomena in a semiconductor under conditions of charge carrier transport in a number of papers. The statistical methods considered can be used for the theoretical analysis of fluctuation phenomena both under equilibrium conditions and in a nonequilibrium stationary state of a system.
