Observation of quantized electron accumulation states at the surface of indium nitride
Smith, Kevin E.1; Colakerol, Leyla1; Jeong, H.K.1; Lukasz, Plucinski1; Alex, DeMasi1; Timothy, Learmonth1; Per-Anders, Glans1; Yufeng, Zhang1; Chen, T.C.1; Moustakas, T.D.1; Alexei, Fedorov1; Piper, Louis1; Veal, Tim2; McConville, Chris2
1United States;
2United Kingdom

The surface and bulk electronic structure of InN(0001) thin films has been studied using high resolution synchrotron radiation excited angle-resolved photoemission spectroscopy (ARPES). The InN thin films were grown by plasma-assisted molecular beam epitaxy on c-plane sapphire. We have measured a series of unusual states in conduction band, near EF. These states are observed for a relatively narrow range of photon excitation energies and angle of detection, and are nested around the Brillouin zone center. The states are identified as due to electron accumulation at the surface, and we have discovered that these are in fact quantum well states. ARPES was also used to measure the Fermi surface of the quantum well states, as well as their constant binding energy contours below EF. The Fermi surface was found to consist of concentric, perfectly circular structures associated with each of two quantum well states, but the corresponding energy contours assume a hexagonal symmetry away from EF. The Fermi level, and the size of the Fermi surface for these quantum well states could be controlled by varying the method of surface preparation. This is the first unambiguous observation that electrons in the InN accumulation layer are quantized, and the first time the Fermi surface associated with such states has been measured.
This work was supported in part by the NSF under grant number DMR-0311792, by the ARO under grant 40126-PH, and by the AFOSR. Experiments were performed at the National Synchrotron Light Source (NSLS) and the Advanced Light Source (ALS). The NSLS is supported by the DOE, Division of Materials and Chemical Sciences, and the ALS by the DOE, Materials Sciences Division under contract no. DE-AC03-76SF00098.
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