E+ transition in GaAs1-xNx and GaAs1-xBix due to isoelectronic-impurity-induced perturbation of the conduction band

An above-band-gap transition E+ is experimentally observed in the dilute GaAs1-xBix alloy. Precise measurements at very low dilutions are made of the above-band-gap transition E+ that is observed in GaAs1-xNx, making it possible to compare the behavior of the different isoelectronic traps Bi and N in the common host GaAs with respect to their perturbation to the host electronic structure. We suggest that the origin of the E+ level observed in GaAs is not the isolated isoelectronic impurity level N-x, as is presumed in the band-anticrossing model, but rather the isoelectronic-impurity-induced perturbation of the conduction band L-6(c).