Study of the Gd/GaAs(110) system: interface and Schottky barrier formationat low and room temperatures

The interface formation upon deposition of Gd overlayers onto n-type GaAs(1 10) substrates was investigated at room and low (20 K, 100 K) temperatures by PE spectroscopy using synchrotron radiation, ultraviolet photoelectron s pectroscopy (UPS), Auger electron spectroscopy (AES), and low energy electr on diffraction (LEED) techniques. Binding energy shifts of Ga 3d and As 3d levels at 300 K and 100 K were observed starting from the minimal Gd covera ge (similar to 0.03 ML). It was found that band bending saturates only afte r metallization of the interface at 1-2 ML. It is argued that two different mechanisms are involved in the Schottky barrier formation: Fermi level pin ning by defect states and metal-induced gap states. The Gd overlayers growt h at low and room temperatures leads to reacted components showing up in Ga 3d and As 3d photoemission spectra at coverages greater than or equal to 0 .03 ML. All components (reacted and unreacted) move to lower binding energi es upon deposition of Gd. LEED studies at T= 20-300 K showed disordered int erface structures at submonolayer and high coverage ranges. Temperature ind uced changes in the interface formation were observed as well. At 300 K the overlayer is cluster-like even at 0.03 ML while at 100 K and 20 K it is of Stranski-Krastanov and layer-by-layer types, respectively. (C) 1999 Publis hed by Elsevier Science B.V. All rights reserved.