A kinetic model for metalorganic chemical vapor deposition from trimethylgallium and arsine

A kinetic model based on the collision theory of chemical reactions is proposed for gallium arsenide (GaAs) metalorganic chemical vapor deposition from trimethylgallium and arsine. A simplified reaction mechanism is incorporated into the model, which includes four heterogeneous deposition reactions: Ga-containing and As-containing species with Ga and As sites, as well as carbon incorporation reactions. An equation for the overall growth rate of the four deposition reactions is derived, which is simplified under the Ga-rich or As-rich growth condition. A discussion about antisite defects leads to the conclusion that As-rich growth produces stoichiometric GaAs. The relation between temperature and arsine/trimethylgallium ratio for As-rich growth is defined. The concept of competitive adsorption is introduced to understand doping and ternary deposition. Carrier concentration for n-type, p-type, and amphoteric doping as a function of deposition conditions is derived. Conversion from p type to n type with arsine/trimethylgallium ratio due to residual carbon is, for the first time, quantitatively explained within the framework of doping. Film composition as a function of deposition conditions in ternary deposition of aluminum-gallium arsenide (Al_1-xGa_xAs) and gallium arsenide-phosphide (GaAs_1-yP_y) is also derived. The distributions of Al and P between gas phase and solid film follow the same physics rule but differ in the nature of impinging species. The quantitative agreement between the model and a wide range of experiments demonstrates the value of this model.