An ultrahigh vacuum, low-energy ion-assisted deposition system for III—V semiconductor film growth

A novel ion-assisted deposition system is described in which the substrate and growing film can be bombarded with high current densities (> 1 m A/cm2) of very low energy (10–200 eV) ions. The system design philosophy is similar to that used in III-V semiconductor molecular-beam epitaxy systems: the chamber is an all-metal ultrahigh vacuum system with liquid-nitrogen-cooled shrouds, Knudsen-cell evaporation sources, a sample insertion load-lock, and a 30-kV reflection high-energy electron diffraction system. III-V semiconductor film growth is achieved using evaporated group-V fluxes and group-III elemental fluxes sputtered from high-purity targets using ions extracted from a triode glow discharge. The discharge also serves as the source of ions to bombard the substrate and growing film, and was shown to provide independent control over the ion current density and energy. Using an In target and an As effusion cell, In As deposition rates R of 2 μm/h have been obtained. Epitaxial growth of In As was observed on both GaSb(100) and Si((100) substrates.