Formation of the Ca/GaAs(110) interface

The morphology, chemistry, and band bending at the Ca/GaAs(110) interface are studied with Auger electron spectroscopy, electron energy-loss spectroscopy, low-energy electron diffraction, x-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy. Ca is found to grow nearly uniformly on GaAs at RT. There is a Ca-Ga exchange reaction at the interface. An intermediate position of the Fermi level (EF) resulting from the formation of adsorbate induced states and native defects is found at low coverage at 0.75-0.9 eV above the top of the valence-band maximum (VBM). An additional shift of Erleading to a final position 0.55 eV above VBM takes place when metallicity develops in the overlayer. The results for this interface support Schottky barrier models based on gap states induced or modified by the metal.