Electrical activation of silicon implanted in semi-insulating GaAs: Role of boron and the midgap electron trap (EL2)

A model based on the constraint of stoichiometry is developed to account for some existing data on the donor activation of silicon ions implanted in semi-insulating, boron-doped GaAs grown by the liquid encapsulated Czochralski method. As a function of increasing implant dose (up to 1013 ions/cm2), three stages of activation are pictured: facilitation by EL2, inhibition by boron, and finally, 100% differential activation when boron is depleted. Possible atomic structures are suggested for the boron-related defects and silicon-related donors. A proposal for using implant measurements to help establish the atomic structure of EL2 is advanced.