Annealing dynamics of arsenic-rich GaAs formed by ion implantation

Abstract

We have investigated the annealing temperature dependence of structural and electrical properties in heavily arsenic implanted GaAs which has a similar amount of excess arsenic to low temperature GaAs (LT-GaAs). The fundamental properties of this material are quite similar to those of LT-GaAs. High resolution x-ray diffraction measurements have revealed that it has an increased lattice constant, which is reduced to the value of bulk GaAs by annealing between 300 and 400 °C. Electrical conduction in this material is dominated by hopping between deep states, which is also reduced by annealing above 350 °C. In samples annealed at temperatures ranging from 600 to 850 °C, the dominant electron trap is EL2; it has been confirmed by resistivity measurements with n-i-n structures that the Fermi level is pinned by EL2. In samples annealed below 500 °C, the dominant electron trap is not EL2 but the U-band, although electron paramagnetic resonance measurements show the existence of a large concentration of the ionized arsenic antisite defect (AsGa+). This supports the notion that the U-band is formed by AsGa defects with slightly modified carrier emission properties compared with EL2.