Decomposition of trimethylgallium on the gallium-rich GaAs (100) surface: Implications for atomic layer epitaxy

The decomposition of trimethylgallium (TMGa) on the gallium-rich (4×6) and (1×6) GaAs (100) surface was studied with temperature programmed desorption, Auger electron spectroscopy, and low-energy electron diffraction. TMGa was found to dissociatively chemisorb on the gallium-rich surfaces, apparently at the gallium vacancies that exist on these surfaces. We have unambiguously identified methyl radicals desorbing from the surface with the maximum rate at ∼440 °C following a saturation TMGa exposure. Since TMGa was shown to decompose on the clean, gallium-rich GaAs (100) surfaces, the self-limiting deposition of gallium during atomic layer epitaxy must be due to the presence of surface methyl groups which inhibit further TMGa dissociative chemisorption.