CHARACTERIZATION OF CA-IMPLANTED GAAS BY PHOTOLUMINESCENCE( ION)

Optical properties of Ca+ ion-implanted GaAs were characterized by pho toluminescence measurements at 2 K. Four new emissions denoted by (Ca0 ,X), g(Ca), SM, and (e,Ca) were found to be produced by Ca incorporati on into GaAs. By changing the Ca dopant concentration and excitation i ntensity, it was revealed that the (Ca0, X) emission is due to exciton s bound to a neutral shallow Ca acceptor, and SM probably originates f rom excitons bound to a Ca impurity in a deep energy level. In additio n, in an impure GaAs substrate, Ca could also form a shallow emission g(Ca), despite the fact that the g emission for well-known shallow acc eptors such as C, Be, and Mg was usually found only in ultrapure GaAs. It was demonstrated that Ca is a shallow acceptor impurity in GaAs wi th a binding energy of 28.4 meV