ANNEALING DYNAMICS OF ARSENIC-RICH GAAS FORMED BY ION-IMPLANTATION

We have investigated the annealing temperature dependence of structura l and electrical properties in heavily arsenic implanted GaAs which ha s a similar amount of excess arsenic to low temperature GaAs (LT-GaAs) . The fundamental properties of this material are quite similar to tho se of LT-GaAs. High resolution x-ray diffraction measurements have rev ealed that it has an increased lattice constant, which is reduced to t he value of bulk GaAs by annealing between 300 and 400 degrees C. Elec trical conduction in this material is dominated by hopping between dee p states, which is also reduced by annealing above 350 degrees C. In s amples annealed at temperatures ranging from 600 to 850 degrees C, the dominant electron trap is EL2; it has been confirmed by resistivity m easurements with n-i-n structures that the Fermi level is pinned by EL 2. In samples annealed below 500 degrees C, the dominant electron trap is not EL2 but the U-band, although electron paramagnetic resonance m easurements show the existence of a large concentration of the ionized arsenic antisite defect (As-Ga+) This supports the notion that the U- band is formed by As-Ga defects with slightly modified carrier emissio n properties compared with EL2. (C) 1995 American Institute of Physics .