Direct determination of the band offset in atomic layer deposited ZnO/hydrogenated amorphous silicon heterojunctions from X-ray photoelectron spectroscopy valence band spectra
- Helmholtz-Zentrum Berlin, Institute for Silicon Photovoltaics, Kekuléstrasse 5, 12489 Berlin (Germany)
The chemical composition and band alignment at the heterointerface between atomic layer deposition-grown zinc oxide (ZnO) and hydrogenated amorphous silicon (a-Si:H) is investigated using monochromatized X-ray photoelectron spectroscopy. A new approach for obtaining the valence band offset ΔE{sub V} is developed, which consists in fitting the valence band (VB) spectrum obtained for a-Si:H with a thin ZnO overlayer as the sum of experimentally obtained VB spectra of a bulk a-Si:H film and a thick ZnO film. This approach allows obtaining ΔE{sub V} = 2.71 ± 0.15 eV with a minimum of assumptions, and also yields information on the change in band bending of both substrate and ZnO film. The band offset results are compared to values obtained using the usual approach of comparing valence band edge-to-core level energy differences, ΔE{sub B,CL} − ΔE{sub B,VB}. Furthermore, a theoretical value for the VB offset is calculated from the concept of charge neutrality level line-up, using literature data for the charge neutrality levels and the experimentally determined ZnO/a-Si:H interface dipole. The thus obtained value of ΔE{sub V}{sup CNL} = 2.65 ± 0.3 eV agrees well with the experimental ΔE{sub V}.
- OSTI ID:
- 22304309
- Journal Information:
- Journal of Applied Physics, Vol. 115, Issue 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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