Effect of indium doping on transient transport phenomena in semi-insulating GaAs

The influence of defect structure on transient transport phenomena was inve stigated in semi-insulating GaAs. undoped and doped with In, grown by the l iquid-encapsulated Czochralsky technique. The change in time after a strong laser excitation of the nonequilibrium photo-Hall effect voltage and the p hotomagnetoelectric effect were used to reveal the influence of In doping i n concentrations of up to greater than or equal to 2 x 10(20) cm(-3). We di d not find additional In levels in the band gap. Nevertheless In doping cau sed significant changes in the behavior of nonequilibrium carrier mobility in the temperature range of 300-420 K, which were not observed in other cry stals, undoped or doped with other dopants. The effect of In becomes pronou nced if its concentration exceeds (6-9) x 10(19) cm(-3). These changes coul d not be explained only by the reduction of the dislocation density. We con clude that apart from this the rearrangement of the microscopic inhomogenei ties must be taken into account. It is supposed that lattice defects become distributed more homogeneously, and appear more probably as small (short-r ange) inhomogeneities instead of large accumulations around dislocations. T his leads to the diminished role of the percolation phenomena. It was demon strated that though doping with in reduces the dislocation density, it can intensify the effect of smaller defects on transport phenomena.