Transient electron transport in indium-doped semiinsulating GaAs

We investigated the effect of In-doping up to a concentration of 2 x 10(20) cm(-3) on transient transport phenomena in semiinsulating liquid-encapsula ted-Czochralski grown GaAs. The changes in time after a strong laser excita tion of the photoconductivity and nonequilibrium Hall mobility were analyze d. We did not find extra energy levels caused by indium. Nevertheless, In-d oping caused significant changes in the behavior of the nonequilibrium mobi lity in the temperature range of 300-420 K, which were not observed in othe r crystals, undoped or doped by other dopants. They could not be explained merely by the reduction of dislocation density caused by In. Besides, the I n-doping was demonstrated to cause the rearrangement of defect inhomogeneit ies. It is considered that lattice defects become distributed more homogene ously and appear more probably as short-range inhomogeneities instead of ac cumulations around dislocations. This diminishes the role of percolation ph enomena and intensifies the effect of smaller defects on carrier transport. (C) 2001 American Institute of Physics.