Numerical investigation of non-ohmic hopping conduction in macroscopically non-homogeneousthin layers. Weak electron-phonon interaction

The current-field and the conductivity-field characteristics of random hopping non-uniform systems in the limit of a weak electron-phonon coupling (band-like hopping transport in disordered solids) have been calculated numerically within the Bottger-Bryksin model. In particular, we consider thin layers placed between two planar Ohmic contacts, with exponential spatial variations in the total centre concentration over the layer thickness. We find that firstly for r-hopping transport in spatially uniform layers the current decreases with increasing field, reaching a constant saturation value, and on increasing the degree of non-uniformity the saturation current becomes lower and secondly both uniform and non-uniform r- epsilon -hopping systems are almost exactly Ohmic in the investigated field range; conductivity decreases on increasing the degree of non-uniformity of the centre distribution. Degree of the layer non-uniformity in the limit of weak electron-phonon coupling are quite different from the dependences in the case of strong electron-phonon coupling. The dependences on the degree of the layer non-uniformity of the centre distribution. The dependences on the degree of the layer non-uniformity in the limit of weak electron-phonon coupling are quite different from the dependences in the case of strong electron-phonon coupling.