Effect of ion beam etching on metal-Si and metal-GaAs barriers

A hot filament ion source was used in this investigation. The ion beam acceleration system consisted of two graphite grids for extraction of a 1 mA cm-2 ion beam density of energy between 500 and 1000 eV. A very low energy ion beam [50-200 eV] with the same current density was obtained by using a <100> single-crystal silicon grid. I-V and C-V measurements of Al-Si Schottky diodes pre-cleaned with a 100 eV ion beam before metal evaporation showed no change in the diode barrier height suggesting minimal surface damage (a barrier lowering). Ion etching of the Si surface at an energy higher than 100 eV leads to lowering of the barrier, with a tendency to saturation at a given energy. The induced damage in Si can be completely annealed at 7000C (as indicated by both I-V and C-V measurements) before metal evaporation. The GaAs surface is more sensitive to ion bombardment than Si. Only Al-GaAs Schottky diodes pre-cleaned with a 50 eV ion beam did not change the barrier height. Any other higher ion energy drastically lowers the potential barrier of the metal-GaAs system. (author)