| The surface chemistry of gallium arsenide and indium phosphide has been investigated using infrared spectroscopy (IR), scanning tunneling microscopy (STM), and ab initio molecular cluster calculations. The work presented here provides the first theoretical framework for studying the reaction sites on compound semiconductor surfaces. These sites consist of dimers and threefold-coordinated atoms in the second layer. Stable clusters of gallium arsenide, i.e., GaxAsyHz, where x, y = 4, 5 and z = 11, 13, are those in which the arsenic dangling bonds are filled, while the gallium dangling bonds are empty. By contrast, stable clusters of indium phosphide, i.e., InxPyHz, where x, y = 4, 5 and z = 10, 11, 13, are those in which the phosphorous dangling bonds are either filled or half filled, and the indium dangling bonds are empty.; The most important contribution of this work is the discovery of a new surface structure, the InP (001)-(2 x 1). The InP (2 x 1) is terminated with a complete layer of phosphorous dimers with a half-filled dangling bond on every other phosphorous atom. The half-filled orbital violate the electron counting model [Pashley, Phys. Rev. B 1989, 40, 10481], and indicate that many more reconstructions are possible on these surfaces than was originally thought.; Excellent agreement is achieved between the molecular cluster calculations and the measured vibrational frequencies of adsorbed hydrogen and arsine on gallium arsenide and indium phosphide (001) surfaces. On both GaAs and InP, mono-hydrogen and di-hydrogen bonds are formed with the three-coordinate, group V atoms and dimers. Conversely, electron deficient bridging hydrides are produced on the group III dimers. These latter species occur in isolated or coupled structures involving two or three metal atoms. In addition, we have elucidated the kinetics and mechanism of arsine decomposition on gallium-rich GaAs (001). The combination of STM, IR, and ab initio molecular cluster calculations provides a powerful tool for investigating the surface physics and chemistry of compound semiconductors. |
