Effect of N₂⁺ Ion Implantation and Thermal Annealing on Near-Surface Layers of Implanted GaAs

The surface of semi-isolating GaAs (100) was irradiated with a fluence of 6×10¹⁷ cm¯² of the N₂⁺ ion beam; then, the samples were thermally annealed at temperatures of 500, 700, and 900°C for 2 h in an argon gas flow. The surface roughness of implanted samples was investigated with the help of atomic force microscopy. Numerous hillocks, which caused a significant increase in surface roughness, were observed. The spectroscopic ellipsometry method was used for determination of pseudo-dielectric functions of the near-surface layers in the investigated samples and the thickness of native oxides covering the irradiated surface. It was observed that the shapes of disorder spectra of the dielectric functions of near-surface layers of implanted GaAs partly returned to their original state after the thermal annealing.