ATOMIC LAYER EPITAXIAL-GROWTH MECHANISM OF A GALLIUM LAYER ON THE (100) AS SURFACE OF GAAS CRYSTALS IN MOVPE

The mechanism of the ALE growth of a Ga layer on the (100) As surface of GaAs crystals in the ordinary MOVPE conditions was investigated by ab initio MO calculations. It was found that the adsorption of an alkyl gallium molecule takes place on the (100) As surface by the coordination of a lone pair of electrons of an As atom which forms the first layer GaAs crystals to the Ga atom of the alkyl gallium approaching the surface. The saddle point structure and the lowest energy reaction path was calculated for the ALE process. The displacements of atoms for the reaction system were shown visually following the reaction path. The theoretically obtained activation energy for the ALE growth ( ∼ 40 kcal/mol) is approximately equal to the observed value for the decomposition of TMG on the growing surface of GaAs crystals in ALE growth experiment ( ∼ 42 kcal/mol), but quite different from the activation energy in the thermal decomposition of TMG in gas phase (64 kcal/mol). © 1990.