RELAXATION OF PERSISTENT PHOTOCONDUCTIVITY IN AL0.3GA0.7AS

Stretched-exponential decay of persistent photoconductivity (PPC) has been observed in Al0.3Ga0.7As in the temperature region T<90 K. The decay time constant and exponent have been measured at different temperatures. Experimental results show that the thermal activated capture of electrons at the DX centers becomes negligible at T<40 K. However, a transition from a thermally activated to a nearly-temperature-independent tunneling capture at a temperature on the order of 40 K has been observed for the first time for Al0.3Ga0.7As, which is consistent with the multiphonon-emission model for DX centers of large lattice relaxation. © 1990 The American Physical Society.