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

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 degrees C. Electrical conduction in this material is dominated by hopping between deep states, which is also reduced by annealing above 350 degrees C. In samples annealed at temperatures ranging from 600 to 850 degrees 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 degrees 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 (As-Ga+) This supports the notion that the U-band is formed by As-Ga defects with slightly modified carrier emission properties compared with EL2. (C) 1995 American Institute of Physics.