Interface and Schottky barrier formation in the Gd/GaAs(110) system

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 photoemission, UPS, AES, and LEED. Binding energy shifts of Ga 3d and As 3d levels at 300 K and 100 K were observed starting from the minimal Gd co verage (similar to 0.03 ML). It was found that band bending saturates only after metallization of the interface at 1-2 hit. It is argued that two diff erent mechanisms are involved in the Schottky-barrier formation: Fermi leve l pinning by defect states and metal-induced gap states. The growth of Gd o verlayer at low and room temperatures leads to reacted components showing u p in Ga 3d and As 3d photoemission spectra at coverages greater than or equ al to 0.03 hit. LEED studies at T = 20 300 K showed disordered interface st ructures at submonolayer and high coverage ranges. Temperature-induced chan ges in the interface formation were observed as well. At 300 K the overlaye r is cluster-like even at 0.03 ML, while at 100 K and 20 R it is close to S transki-Krastanov and layer-by-layer types, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.