Effect of 20–95 eV Ar ion bombardment of GaAs(001): In pursuit of damage-free ion-assisted growth and etching

Defect generation due to very-low-energy ion bombardment of GaAs(00l) has been studied. Ar⁺ bombardment was performed at energies E = 20–95 eV and current densities J= 0.1 -0.75 mA/cm² on surfaces maintained at 615 °C in an As₄ flux, both without growth and during GaAs molecular beam epitaxy. Reflection high-energy electron diffraction patterns exhibited 2×4 reconstruction and strong Kikuchi lines, indicative of flat ordered surfaces, independent of E and J. Cross-sectional transmission electron microscopy showed that subsurface dislocation loops were generated when 55 eV. The defect density increased with increasing E and J. Films grown withE≤50 eV were free of extended defects, showing that the beneficial effects of ion-assisted molecular beam epitaxycan be achieved without causing ion damage. Measurable sputtering rates were observed forE≤50 eV at J=0.5 mA/cm².