SCLC-noise as a statistical carrier correlation effect

Abstract

1. THE NOISE problem under SCLC conditions is beset with many serious difficulties pertaining either to the strong coulomb interaction between carriers or to the interplaying of the different types of noise. The author attempted to solve the problem in a more fundamental manner, namely within the frame of the general (markoffian) noise theory [l]. The primary fluctuating quantity being the current (density) i, the method proceeds by expressing it in terms of the (markoffian) variables of the system, the noise problem being thus essentially reduced to the calculation of the statistical correlations between these variables. As the basis of the method has been presented elsewhere [2,3], we limit ourselves in this report to a very condensed outline and concentrate on a critical appraisal of the theory and of its results. The following limitations are introduced throughout: (a) neglect of the displacement current idisPl (i.e. continuity of the conduction current &,d), which implies a restriction to low frequencies according to Wrdier 4 1 in a quasineutral solid or to wrt, 6 1 in SCL solids (Tag, = dielectric relaxation time, rtr = transit time); (b) one dimensional problem (a solid of length 15); (c) vanishing of the electric field at the injecting electrodes. Moreover, the formulae quoted below refer to the one carrier (electron) trap free case, to be approximately achieved in very pure dielectrics, compensated semiconductors with small capture cross section of the impurity atoms and trap filled semiconductors at high injection levels. Other cases, including the quasineutral semiconductors, are treated in the literature[3,4] and are occasionally referred to below. 2. There is no unique choice of the markoffian variables, but the local concentration n(x, t) and velocity v(x, t) seem the most adequate (u(x, t) is defined as the local average