| AVS 62nd International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS+AS+EM+EN-ThA |
| Session: | Atomistic Modeling of Surface Phenomena & Semiconductor Surfaces and Interfaces - II |
| Presenter: | Rainer Timm, Lund University, Sweden |
| Authors: | R. Timm, Lund University, Sweden M. Hjort, Lund University, Sweden J. Knutsson, Lund University, Sweden O. Persson, Lund University, Sweden A. Troian, Lund University, Sweden S. Lehmann, Lund University, Sweden K.A. Dick, Lund University, Sweden A. Mikkelsen, Lund University, Sweden |
| Correspondent: | Click to Email |
InAs is known to typically show n-type behavior with an electron accumulation layer at the surface. Many studies have been performed for evaluating to which extend this behavior is due to adsorbates such as a native oxide layer, or to specific surface orientations and reconstructions of clean InAs. InAs nanowires (NWs) add an extra degree of complexity, since they can exist both in zincblende and wurtzite crystal structure, typically exhibiting unintended switching between both stacking orders during epitaxial growth. During recent years, a strong debate has been going on about how far such crystal phase mixing influences the conductivity of InAs NWs and therewith their suitability for high-mobility device application [1]. A staggered band alignment with band offsets in the range of up to 0.1 eV between zincblende and wurtzite conduction band edges has been reported, based on transport measurements in ambient atmosphere [2]. In contrast, our recent study of clean and unreconstructed InAs NW surfaces based on scanning tunneling microscopy and spectroscopy (STM/S) in ultrahigh vacuum showed aligned conduction band edges for zincblende [110[ and wurtzite [11-20[ surfaces [3].
Here, we present a systematic study of surface band-bending upon cleaning and oxidation of various InAs surfaces, including purely zincblende or purely wurtzite NWs, obtained by synchrotron-based X-ray photoemission spectroscopy (XPS). We were able to clean all investigated InAs surfaces from their native oxide by annealing them in the presence of atomic hydrogen [3]. Different rates of cleaning and re-oxidation were observed for the different surfaces. Even more importantly, from the energy shifts of the investigated core-levels upon oxidation, varying between 0.1 and 0.3 eV for various surfaces, we obtained significant differences in oxide-induced surface band-bending for different surface orientations. We will compare our XPS results with the atomic and local electronic structure of the specific surfaces as obtained by STM/S [4]. Our results indicate that the band alignment along InAs heterostructures, and therewith the transport properties of InAs NWs, depend on the surface orientation, composition, and atomic structure rather than the crystal phase of the specific InAs segments.
[1] Thelander et al., Nano Lett. 11, 2424 (2011)
[2] Dayeh et al., Adv. Funct. Mater. 19, 2102 (2009)
[3] Hjort et al., ACS Nano 12, 12346 (2014)
[4] Knutsson et al., ACS Appl. Mater. Interfaces 7, 5748 (2015)