Quantum structure of adsorbates on semiconductor surfaces

Polarization-dependent angle-resolved photoemission spectroscopy with synchrotron radiation was performed for Ge adatom on GaAs(110) surfaced in the monolayer regime. Chemisorbed states at the gamma point in the Brillouin zone were observed about 6.8 eV below the valence band maximum. The states are attributed to chemisorption states that are precursors ot Ge/GaAs heterojunction interface states which are theoreticallY predicted. A special low temperature UHV manipulator was constructed and used to perform oxygen and Co physisorbtion experiments on GaAs(110) at about 45 K.