Drastic change in electronic structure of AlGaN under Ba adsorption

Abstract

A 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)

Synchrotron radiation photoemission study of the electronic structure of the ultrathin K/AlN interface

“…For the clean AlN surface the spectrum is characterized by the weakly structured band in the binding energy region of −3−12 eV below E VBM with major VB maximum at ∼ 4.0 eV. The shape and the bandwidth of the valence band spectrum coincide well with the GaN and AlGaN photoemission results reported earlier [11][12][13][14][15]. It can be seen that a K 3p peak appears in the spectrum at binding energy of ∼ 15.3 eV and increases upon the adsorption of potassium.…”

“…A new ISS peak was found at the energy of 6.6 eV with a K 0.9 ML coverage. This can be caused by the surface state caused by the adsorption of K. Similar data on the induced surface states near EVBM were obtained for the Cs/GaN, Ba/GaN, Ba/InGaN, Ba/Al 0.16 Ga 0.84 N, Ba/Al 0.42 Ga 0.58 N interfaces [11][12][13][14][15]. Fig.…”

“…The electronic structure of the AlN surface has been studied in many aspects [3][4][5], but information on structure and electronic properties of metal/AlN interface is very limited [6][7][8][9][10]. Recently, the electronic and photoemission properties of metal/Al x Ga 1−x N interfaces, namely Cs/GaN, Ba/GaN, Ba/InGaN, Ba/Al 0.16 Ga 0.84 N, Ba/Al 0.42 Ga 0.58 N, have been investigated [11][12][13][14][15].…”

Synchrotron radiation photoemission study of the ultrathin Cs/InN interface

“…For III nitrides, accumulation layers were revealed at the clean InN surface [23,24] and formed via adsorption at both the GaN and AlGaN surfaces [28,29]. Adsorption of alkali metals Cs, K on the InN surface has been recently investigated in [21,26,27] in which the significant modification of the surface electronic structure has been demonstrated.…”