Angle‐resolved photoelectron spectroscopy study of the GaN(0001)‐2×2 surface

Abstract

GaN(0001)‐2×2 surfaces were investigated by angle‐resolved ultraviolet photoelectron spectroscopy (ARUPS) as well as X‐ray photoelectron spectroscopy (XPS). Contamination‐ and metal‐free GaN thin films with a 2×2 reconstruction and a rms roughness below 1 nm were grown on 6H‐SiC(0001) by plasma assisted molecular beam epitaxy (PAMBE). The valence band structure of the surface was investigated in‐situ with ARUPS along the $ {\bar \rm \Gamma} - {\bar \rm M}$ and $ {\bar \rm \Gamma} - {\bar \rm K}$ directions of the surface Brillouin zone. Weak dispersive surface states related to the unreconstructed GaN surface or to the 2×2 superstructure as well as the dispersion of electron states of the bulk band structure are identified and compared to available results from density functional theory (DFT) calculations [Phys. Rev. B 77, 115120 (2008)] for GaN(0001). (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Drastic change in electronic structure of AlGaN under Ba adsorption

“…Energy position of E VBM with respect to the Fermi level E F corresponds to 3.2 eV [12]. Based on the data about the surface states spectrum for the GaN(0001) surface [3][4][5][6][7][8][9][10], we assume that analogues states at the n-Al 0.16 Ga 0.84 N(0001) surface are responsible for the shape of the spectra (see Fig. 2).…”

“…The electronic structure of GaN(0001) has been a subject of the number of experimental [3][4][5][6] and theoretical [7][8][9][10] investigations. The surface related features in the energy range of the valence band have been studied by using ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS).…”

Electron microscopy and ultraviolet photoemission spectroscopy studies of native oxides on GaN(0001)

“…3(a), the peak energy in the VBM region of the native oxide on GaN(0001) is located ∼5.7 eV below E F ; that of clean GaN(0001) is located 4.0-4.5 eV below E F . [10][11][12] Note that Refs. 10-12 describe results for surfaces grown via molecular beam epitaxy (MBE) and characterized using UPS in situ; therefore, the possibility of surface oxidation can be excluded.…”