The Effect of Surface Oxides on the Creation of Point Defects in GaAs Studied by Slow Positron Beam

Abstract
The depth distributions of the positron annihilation in as-etched GaAs before and after the air exposure were characterized by a slow positron beams. The characteristic value of S parameter at near-surface region is decreased after the air exposure of the etched-GaAs, which indicates that the thin oxide layer is formed on the fresh surface of the etched GaAs during the air exposure. It is found that the mean diffusion length of positrons is not changed after the as-etched GaAs was exposed to air atmosphere. This implies that the trapping centers for a positron are not created below the surface by the chemisorption of oxygen atoms.