Surface monitoring and enhancement of crystal growth with in situ ion bombardment during semiconductor epitaxy

In situ ion bombardment has been used to monitor and enhance epitaxial crystal growth. Particular focus is on the use of glancing-angle ions and the advantages of this geometry compared to normal incidence ion bombardment. The glancing-angle geometry constrains ion momentum primarily in the growth plane, uniquely coupling it to surface defects and providing a highly surface sensitive tool.; At low ion currents, glancing-angle ion scattering was an unobtrusive probe of submonolayer growth dynamics during GaAs(001) molecular beam epitaxy. Features of the specular ion current behavior under dynamic growth conditions were correlated with surface defect populations and processes, and integration of a linear defect-ion scattering model with kinetic rate equation growth simulations allowed quantitative analysis. The nucleation, growth, and coarsening stages were detected in real-time, and statistical analysis of adatom, step-edge, and island densities agreed well with previous measurements by STM.; At higher ion currents, ion-enhanced surface diffusion and epitaxial growth were demonstrated as ion-adatom arrival rate ratios were increased up to 0.25. During the molecular beam epitaxial growth of GaAs(001), the average adatom lifetime decreased monotonically with increasing ion current density, growth oscillations were suppressed as the growth mode transitioned to step-flow, and surface roughness was decreased from 0.5 to 0.25 nm in the ion-assisted films. Similar surface smoothening from 11 to 0.5 nm was achieved during the low temperature epitaxial growth of ZnO/Al2O3(0001), and the films were densified by the ions without increasing the residual compressive stress.; The low temperature epitaxial growth of ZnO/Al2O3(0001) during reactive magnetron sputtering was also studied. The unique attainment of epitaxial growth on unheated substrates in this highly refractory system is ascribed to two factors: (1) the high mobility of unreacted Zn and (2) the ion bombardment energy input afforded by the plasma. This is supported by evidence that two critical parameters determine the film properties: (1) the Zn/O ratio and (2) the ion-adatom arrival rate ratio. Normal incidence ions improved film smoothness and quality but increased residual stress.; Glancing-incidence ions are a unique probe of epitaxial growth and may provide a new alternative for film densification that minimizes deleterious bombardment effects.