Hydrodynamic modeling of charge carrier transport and transverse pattern formation in ZnS:Mn thin-film electroluminescent structures

Abstract

The charge carrier transport and transverse pattern formation in ac-driven thin-film electroluminescent devices are studied on a hydrodynamic level. A set of model equations is set up to describe the coupled dynamics of the charge carriers and the local lattice temperature. Assuming a laterally homogeneous system, the number and stability of stationary states is analyzed in one-dimensional simulations. Starting from laterally inhomogeneous initial conditions, the formation and dynamics of transverse patterns is studied in two-dimensional simulations. The influence of frequency and amplitude of the applied voltage as well as of the relative time scales of thermal and electrical transport on the results is investigated. Depending on the parameters, we find a variety of different patterns, such as localized high- or low-current filaments, temporally or spatially oscillating solutions, and moving high-field domains. The results are interpreted on the basis of null cline diagrams for the space charge and lattice temperature dynamics. The two-dimensional patterns are compared to luminescence patterns that were found in various experiments.