Site-Specific Chemistry of Gallium Arsenide Metalorganic Chemical Vapor Deposition

Herein, we summarize our studies of the surface chemistry of gallium arsenide as it pertains to the metalorganic chemical-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(CH 3 ) 3 or AsH 3 ) creates the site for the decomposition of the other molecule (AsH 3 or Ga(CH 3 ) 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 site-specific 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.