CHARACTERIZATION OF CA+ ION-IMPLANTED GAAS BY PHOTOLUMINESCENCE

Optical properties of Ca+ ion-implanted GaAs were characterized by photoluminescence measurements at 2 K. Four new emissions denoted by (Ca0,X), g(Ca), SM, and (e,Ca) were found to be produced by Ca incorporation into GaAs. By changing the Ca dopant concentration and excitation intensity, it was revealed that the (Ca0, X) emission is due to excitons bound to a neutral shallow Ca acceptor, and SM probably originates from excitons bound to a Ca impurity in a deep energy level. In addition, 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 acceptors 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 with a binding energy of 28.4 meV