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HL: Fachverband Halbleiterphysik

HL 81: Focus Session: Extended defects in semi- and nonpolar GaN II

HL 81.2: Talk

Thursday, March 14, 2013, 15:00–15:15, H13

Electronic states at nonpolar GaN surfaces investigated by photoelectron spectroscopy and optical anisotropy spectroscopy — •Marcel Himmerlich¹, Anja Eisenhardt¹, Jochen Räthel², Eugen Speiser², Norbert Esser², and Stefan Krischok¹ — ¹Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, 98684 Ilmenau, Germany — ²Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Straße 9, 12489 Berlin, Germany

In-situ investigations were carried out on homoepitaxially grown nonpolar m-plane (1-100) and a-plane (11-20) GaN surfaces. Occupied surface states 3.1 and 3.2 eV below the Fermi energy are identified using photoelectron spectroscopy (PES). These states are involved in anisotropic optical transitions at photon energies of 3.2 and 3.3 eV for the m-plane and a-plane configurations, respectively, as confirmed by reflection anisotropy spectroscopy (RAS). Additionally, an optical transition at 4.7 eV was found in RAS. Excitonic and electronic surface band contributions in the RAS measurement were disentangled by comparing spectra of clean and oxidized surfaces. The experimental results are compared to calculated surface band structures from the literature. Furthermore, the influence of oxidation on the surface electronic properties and the correlated optical properties was also investigated. Besides degradation of the initial surface states, a reduction of the upward bend bending by 0.4 eV is found for both cases.