Field dependent equilibrium energetic distribution of localized charge   carriers in disordered semiconductors at low temperatures
  The hopping transport of charge carries in 3-dimensional disordered semiconductors is analyzed in this work. It is assumed that the density of localized states is a decreasing function of energy and contribution of thermoactivated jumps into the transport is negligible. The possibility of equilibrium energetic distribution for this case is shown. This distribution is characterized by field--dependent effective temperature. 
D.V. Nikolaenkov, V.I. Arkhipov and V.R. Nikitenko