Drastic change in electronic structure of AlGaN under Ba adsorption

Abstract

AbstractA synchrotron‐radiation photoemission spectroscopy is applied to the clean and Ba‐deposited AlGaN(0001) surfaces to investigate the interface electronic structure relevant to both the surface states and an electron accumulation layer and to clarify their origins. Valence‐band photoemission and Ga 3d, Al 2p, Ba 4d core level spectra of AlxGa1‐xN (x=0.16, x=0.42) have been studied under the step‐by‐step Ba submonolayer deposition. The clean n ‐Al0.16Ga0.84N surface exhibits the surface states at energies of 2.8 eV, 5.5 eV, and 7.8 eV with respect to the valence band maximum, while the states for the clean Al0.42Ga0.58N surface are at higher energies of 3.9 eV, 5.6 eV, and 8.2 eV. Drastic change in the valence band spectra is revealed and it is showed that narrowing of valence band and suppression of surface states occur with increasing Ba coverage. The appearance of a new photoemission peak at the Fermi level clearly indicates the creation of the accumulation layer on the n ‐Al0.16Ga0.84N surface under the Ba adsorption. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)