Site-specific chemistry of gallium arsenide metalorganic chemical vapor deposition

Herein, we summarize our studies of the surface chemistry of gallium arseni de as it pertains to the metalorganic chemical-vapor deposition of compound semiconductors. It has been found by scanning tunneling microscopy and vib rational spectroscopy that the adsorption of reactant molecules on reconstr ucted GaAs (001) surfaces is "site-specific." Trimethylgallium dissociative ly adsorbs only on arsenic sites, whereas arsine dissociatively adsorbs onl y on gallium sites. The decomposition of one precursor molecule (Ga(CH3)(3) or AsH3) creates the site for the decomposition of the other molecule (AsH 3 or Ga(CH3)(3), respectively). In this fashion, the crystal grows one atom ic layer at a time. Studies of carbon doping with carbon tetrachloride have shown that adsorbed chlorine attacks the exposed gallium and generates vol atile GaClx species. The site-specific nature of this reaction leads to a d ramatic change in the film morphology, with the formation of 30-nm etch pit s randomly distributed over the surface.