ARXPS analysis of surface compositional change in Ar+ ion bombarded GaAs (100)

Angle-resolved x-ray photoelectron spectroscopy (ARXPS) has been used to study surface compositional changes in GaAs (100) as a consequence of 1 to 5 keV Ar+ ion bombardment. Prior to Ar+ ion bombardment, the ARXPS measurements showed that neglecting surface contamination, the composition of the GaAs surface was close to its stoichiometric value of 1:1. After Ar+ ion bombardment, the oxide layer was efficiently removed. At steady state the altered layers induced by 1-5 keV Ar+ ion bombardment were, on average, Ga-rich up to the sampling depth of the ARXPS technique. The ARXPS measurements also showed that the depth profile of the altered layer was a function of Ar+ ion energy. The altered layer induced by 1 keV Ar+ ion bombardment was inhomogeneous as a function of depth and appeared richer in Ga on the surface than in the subsurface region, that by 3 keV Ar+ ion bombardment was homogeneous and that by 5 keV Ar+ ion bombardment was less Ga-rich on the surface than in the subsurface region. The results are discussed in the context of preferential sputtering, radiation-enhanced diffusion/segregation, and altered layer thickness dependence on Ar+ ion energy.