Band bending, chemistry and morphology of gallium arsenide(100) surfaces and interfaces with oxygen, sulfur, and metals

Understanding and controlling the properties of the GaAs surface and its interfaces with other materials is a key issue concerning GaAs technology. In this work, the GaAs (100) surface and it's interfaces with other materials were studied on an atomic scale using ultraviolet photoemission spectroscopy. The interfaces of GaAs (100) with oxides, sulfides, metals, and semimetals were studied. Since atomically clean (100) surfaces cannot be obtained by cleaving in UHV, different methods of preparing the surfaces were also studied.; Clean surfaces were obtained by either heating away thin oxides, or by heating to remove a thicker As cap grown in an MBE chamber. In the oxide case, it was found that clean surfaces can be obtained at relatively low annealing temperatures if care is taken to avoid the formation of refractory Ga{dollar}sb2{dollar}O{dollar}sb3.{dollar} Removal of the thick As cap was studied as a function of the final annealing temperature. It was found that a wide range of surface stoichiometries can be seen between 300{dollar}spcirc{dollar}C and 600{dollar}spcirc{dollar}C. The electronic structure of these surfaces was studied, and the core level lineshapes were deconvolved into their surface and bulk components.; The GaAs (100)/sulfide interface was studied in terms of the sulfide being an electrically "passivating layer". These layers have been shown to drastically reduce the electron-hole surface recombination velocity (SRV) relative to the native oxide, albeit only temporarily (a few hours). The chemical bonding, stoichiometry, gross structure, and band bending were investigated. A model which correlates these various issues, particularly the strange band bending and SRV is proposed and shown to be consistent with a wide range of experiments.; Metal and semimetal overlayers were studied on As cap prepared surfaces. The growth of Al and Au on the 580{dollar}spcirc{dollar}C annealed surface are of particular interest, as these were previously reported to have extremely low and high Schottky barriers, respectively. The previous reports are found to be incorrect due to surface photovoltage and alloying effects. The growth of Ag, In, Bi, and Sb overlayers were studied in terms of the morphology and electronic structure of the overlayers.