OPTICAL AND ELECTRICAL-PROPERTIES OF DISORDERED LAYERS IN GAAS CRYSTALS PRODUCED BY SI+-ION IMPLANTATION

The ion dose dependence and the annealing behavior of GaAs after implantation with 200 keV 2 multiplied by 10**1**2-2 multiplied by 10**1**6 Si** plus ions/cm**2 as studied by using optical absorption, reflection, photoluminescence, sheet-resistivity, Hall effect and field effect methods. The experimental results of the optical absorption and reflection indicate that, when annealed at about 400 degree C, the disordered layers produced by high-dose implantation reorder epitaxially on the underlying crystal, leaving relatively little residual disorder in the near-surface. However, 800 degree C annealing is required for perfect recrystallization. The temperature dependence of the sheet-resistivity indicates that, next to the variable-range hopping and phonon-assisted hopping regions, a new region is observed. Holes, thermally-activated from localized states near the Fermi level E//F to the mobility edge E//V near the valence band, are responsible for electrical conduction in this region.