Direct observation of Levy flight of holes in bulk n-InP
  We study the photoluminescence spectra excited at an edge side of n-InP slabs and observed from the broadside. In a moderately doped sample the intensity drops off as a power-law function of the distance from the excitation - up to several millimeters - with no change in the spectral shape.The hole distribution is described by a stationary Levy-flight process over more than two orders of magnitude in both the distance and hole concentration. For heavily-doped samples, the power law is truncated by free-carrier absorption. Our experiments are near-perfectly described by the Biberman-Holstein transport equation with parameters found from independent optical experiments. 
Serge Luryi, Oleg Semyonov, Arsen Subashiev, and Zhichao Chen
cond-mat.stat-mech