ArF excimer-laser-stimulated growth of polycrystalline GaAs thin films

Abstract

The growth of GaAs thin films by a laser photodecomposition process is reported. Ga(CH3)3 and As(CH3)3 mixtures are photolyzed above (100) Si and GaAs substrates by a 193-nm argon fluoride excimer laser beam directed normal to the substrate surface. Gas-phase products diffuse to, and stick on the surface where further laser irradiation leads to the formation of polycrystalline GaAs, with grain sizes between ∼20 and 2000 Å. Deposited films contain ∼1–3 at. % carbon, as determined by Auger electron spectroscopy. Surface irradiation by the transmitted beam improves the optical constants of the film to values approaching bulk GaAs, but annealing is not sufficient to promote epitaxial growth at fluences as high as 70 mJ/cm2, for average substrate temperatures up to 400 °C. Laser irradiation of the GaAs substrates exposed to BCl3 or As(CH3)3 immediately prior to deposition removes the native oxide and carbon contamination.