Experimental Evidence for the Spatial Correlation of Charged EL2(+) Defects and Acceptors in Semi-insulating GaAs

The far-infrared photoconductivity due to shallow donors was measured in semi-insulating GaAs for different states of the EL2 defect - normal, metastable, and during the transition - with and without hydrostatic pressure. The results show that the intra-donor transition line broadening observed previously after transferring the EL2 to the metastable configuration cannot be due to lattice distortion effects, and can only be explained in terms of a spatial correlation of charged EL2(+) and acceptor A(-) states, which form electric dipoles.