Unusual evolution of the lowest unoccupied state in Ga(As0.5-yP0.5-yN2y)

The character of the lowest unoccupied state in the random Ga(As0.5-yP0.5-yN2y) alloys is investigated for small nitrogen concentrations (0.1%<2y<1.0%) using a pseudopotential technique. As nitrogen is added to Ga(As0.5P0.5), this state evolves from an impurity localized level to a delocalized bandlike state. This evolution involves two processes. The first process is an anticrossing between the deep-gap nitrogen impurity level existing in the dilute alloy limit y-->0 and the Gamma (1c)-like extended state of Ga(As0.5P0.5). The second process is the formation of an impurity subband due to the interaction of the deep-gap nitrogen levels. These two processes are expected to occur in any Ga(As1-x-y1 Px-y2Ny1 + y2) alloys for which x is larger than 0.3.