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HL: Fachverband Halbleiterphysik
HL 4: III-V semiconductors: mainly wells and surfaces
HL 4.10: Vortrag
Montag, 11. März 2013, 12:00–12:15, H15
Influence of adsorbates on the surface electronic properties of polar InN — •Anja Eisenhardt, Stephanie Reiß, Stefan Krischok, and Marcel Himmerlich — Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, 98684 Ilmenau, Germany
Thin stoichiometric InN(0001)-2×2 (In-polar) and InN(000-1) (N-polar) samples were grown by plasma-assisted molecular beam epitaxy and in-situ characterized by photoelectron spectroscopy (XPS, UPS). While the InN(0001)-2×2 surface shows a valence band maximum (VBM) to Fermi-level distance (EF - VBM) of 1.4 eV, indicating a strong surface electron accumulation, the band bending at the InN(000-1) surfaces is reduced (EF - VBM ∼ 1.0 eV). This difference can be microscopically explained by surface states that influence the position of the surface Fermi level. For InN(0001)-2×2 they are located above the conduction band minimum while at InN(000-1) an occupied surface state is located at the VBM. We will show how the interaction with adsorbates (especially oxygen and water) and the corresponding dipole formation change the surface electronic properties and the band alignment at InN surfaces. At In-polar InN surfaces, oxygen adsorbates as electron acceptors strongly reduce the electron accumulation due to the interaction with the free dangling bonds of the In-adatoms. At N-polar InN surfaces, oxygen has no further impact on the already reduced band bending. Water instead tends to increase the downward band bending at N-polar InN surfaces, while it has minor effect on the initial band alignment at In-polar InN surfaces.