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O: Fachverband Oberflächenphysik
O 84: Photovoltaics (jointly with CPP, DS and HL)
O 84.13: Vortrag
Freitag, 15. März 2013, 12:30–12:45, H2
Valence band offsets estimation of Al2O3 films on silicon by XPS and UPS measurements — •Johannes Ziegler1, Volker Naumann2, Martin Otto1, Alexander Sprafke1, and Ralf B. Wehrspohn1,3 — 1Martin-Luther-University Halle-Wittenberg, Institute of Physics, Halle, Germany — 2Fraunhofer Center for Silicon Photovoltaics CSP,Halle, Germany — 3Fraunhofer Institute for Mechanics of Materials Halle, Halle, Germany
A quantitative measurement of valence band offsets in isolator-silicon junctions might help to realize heterojunction devices such like semiconductor-isolator-semiconductor (SIS) solar cells. We measured XPS and UPS spectra of thin (2–50 nm thick) Al2O3 films deposited on silicon by thermal ALD. The valence band offsets of these structures are estimated from the XPS spectra using the method of Kraut et.al. [1] . A slight trend in the valence band offsets 3.3–4.5 eV with increasing film thickness 2–50 nm was calculated from the XPS spectra. To estimate the valence band offsets from the UPS spectra 3.3–3.4 eV of 2–10 nm thick Al2O3 on silicon, a simple straight forward approach based on linear regression of the spectra on the band edges is used. We compare the results of both measurements and discuss possible sources for the measured increase of the valence band offset with increasing Al2O3 film thickness.
[1] A. Kraut, R. W. Grant, J. R. Waldrop and S. P. Kowalczyk, Phys. Rev. Lett. 44,p.1620 (1982), http://link.aps.org/doi/10.1103/PhysRevLett.44.1620