Site-specific chemistry of gallium arsenide metalorganic chemical vapor deposition

Abstract
Herein, we summarize our studies of the surface chemistry of gallium arsenide as it pertains to the metalorganic chernical-vapor deposition of compound semiconductors. It has been found by scanning tunneling microscopy and vibrational spectroscopy that the adsorption of reactant molecules on reconstructed GaAs (001) surfaces is "site-specific." Trimethylgallium dissociatively adsorbs only on arsenic sites, whereas arsine dissociatively adsorbs only on gallium sites. The decomposition of one precursor molecule (Ga(CH₃)₃ or AsH₃ creates the site for the decomposition of the other molecule (AsH₃ or Ga(CH₃)₃, respectively). In this fashion, the crystal grows one atomic layer at a time. Studies of carbon doping with carbon tetrachloride have shown that adsorbed chlorine attacks the exposed gallium and generates volatile GaCl_x species. The sitespecific nature of this reaction leads to a dramatic change in the film morphology, with the formation of 30 nm etch pits randomly distributed over the surface.