2013
Volume 13, Number 4, pp. 131–134
Synchrotron photoemission studies of surface electronic structure of III-nitride semiconductors
G.V. Benemanskaya,1 M.N. Lapushkin,1 S.N. Timoshnev,1 A.V. Gigineishvili,2 G.N. Iluridze,2 P.J. Kervalishvili2 and T.A. Minashvili2
1 Ioffe Physical Technical Institute, 194021 St Petersburg, Russia
2 Georgian Technical University, Tbilisi, Georgia
A synchrotron-radiation photoemission study of the electronic structure of group III-nitrides n-GaN (0001) and n-Al0.16Ga0.84N (0001) crystallizing in the wurtzite form is presented. The process of interface formation at Ba-decorated GaN and AlGaN surfaces was investigated to ascertain the electronic interface structures relevant to finding the origins of both the surface states and the electron accumulation layer. Valence band photoemission and Ga 3d, Al 2p and Ba 4d core level spectra of GaN and AlGaN were studied under step-by-step Ba submonolayer adsorption. Surface states were revealed at energies, relative to the valence band maximum, of –0.4, 2.7, 5.0 and 6.5 eV for clean GaN and 2.8, 5.5 and 7.8 eV for clean AlGaN. Dramatic changes in the valence band spectra were observed, suppression of surface states occurs with increasing Ba coverage up to 1 monolayer. The appearance of a new photoemission peak at the Fermi level clearly evidences accumulation layer creation at the n-GaN and n-Al0.16Ga0.84N surfaces.
Keywords: accumulation layer, electronic surface structure, metal/III-nitride interface, photoemission spectroscopy, III-nitride