Decomposition mechanism of arsine on GaAs (001)-(4x2)

     Arsine has been extensively used in MOCVD growth of gallium arsenide-based electronic devices.  To improve the epitaxy growth process, one needs to understand the adsorption and decomposition mechanism of AsH₃ molecule on the GaAs (001) surface.
     By using infrared spectroscopy, scanning tunneling microscopy, and ab initio molecular calculation, we have determined the sequential decomposition mechanism of AsH₃ on the gallium-rich GaAs (4x2) surface.  Particularly, we have found that the the rate-limiting step of AsH₃ dissociation is the initial cleavage of As-H bond and transfer of H to the second-layer arsenic-site.  Shown above are the molecular models for this elemental reaction.  The theoretical calculation found that an activation energy of 16 kcal/mol has to be overcome in order for this reaction to proceed.  This result is in excellent agreement with the kinetic analysis of isotherms obtained from experiment.

This work has been recently reported on J. Phys. Chem. B

1. Fu, Q., Li, L., Li, C. H., Law, D. C., Begarney, M. J., and Hicks, R. F., "Arsine Adsorption on the Gallium-Rich GaAs (001) (4x2) Surface," J. Phys. Chem. B, 104, 5595-5062, 2000.