Tag: CVD

Halide/Hydride vapor phase epitaxy

Gallium Monochloride precursor

In typical HVPE process for GaN deposition gallium monochloride GaCl and ammonia NH₃ are used as precursors of gallium and nitrogen:

GaCl+NH₃=GaN+HCl+H₂

The reaction is exothermic, and the reaction driving force decreases with increasing temperature:

GaCl + NH3 = GaN + HCl + H2 Gibbs Energy and Enthalpy

GaCl + NH3 = GaN + HCl + H2 deposition reaction equilibrium constant

Typical deposition temperature for epitaxial growth is 800-1100°C. At lower temperatures the deposition rate decreases due to reaction kinetic limitation, at higher temperatures the deposition rate decreases as a result of a decrease in supersaturation:

Gallium trichloride precursor

GaN deposition by  reaction of gallium trichloride GaCl₃ and ammonia

GaCl₃ + NH₃ = GaN + 3HCl

is endothermic and the reaction driving force increases with increasing temperature, that makes possible to deposit GaN at temperatures 1300-1400°C:

GaCl3 + NH3 = GaN + 3HCl reaction Gibbs free energy and enthalpy

GaCl3 + NH3 = GaN + 3HCl reaction equilibrium constant

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Murakami, H., Takekawa, N., Shiono, A., Thieu, Q. T., Togashi, R., Kumagai, Y., … & Koukitu, A. (2016). Tri-halide vapor phase epitaxy of thick GaN using gaseous GaCl3 precursor. Journal of Crystal Growth, 456, 140-144.