Detailed photoluminescence studies of thin film Cu{sub 2}S for determination of quasi-Fermi level splitting and defect levels
- Institute of Physics, Carl von Ossietzky University Oldenburg, 26111 Oldenburg (Germany)
- Surface Science Division, Institute of Materials Science, Technische Universität Darmstadt, Petersenstraße 32, 64287 Darmstadt (Germany)
We have studied chalcocite (Cu{sub 2}S) layers prepared by physical vapor deposition with varying deposition parameters by calibrated spectral photoluminescence (PL) and by confocal PL with lateral resolution of Δ x≈0.9 μm. Calibrated PL experiments as a function of temperature T and excitation fluxes were performed to obtain the absolute PL-yield and to calculate the splitting of the quasi-Fermi levels (QFLs) μ=E{sub f,n}−E{sub f,p} at an excitation flux equivalent to the AM 1.5 spectrum and the absorption coefficient α(ℏω), both in the temperature range of 20 K≤T≤400 K. The PL-spectra reveal two peaks at E{sub #1}=1.17 eV and E{sub #2}=1.3 eV. The samples show a QFL-splitting of μ>700 meV associated with a pseudo band gap of E{sub g}=1.25 eV. The high-energy peak shows an unexpected temperature behavior, namely, an increase of PL-yield with rising temperature at variance with the behavior of QFL-splitting that decreases with rising T. Our observations indicate that, contrary to common believe, it is not the PL-yield, but rather the QFL-splitting that is the comprehensive indicator of the quality of the excited state in an illuminated semiconductor. A further examination of the lateral variation of opto-electronic properties by confocal PL and the surface contour shows no detectable correlation between Cu{sub 2}S grains/grain boundaries and the PL-yield or QFL-splitting.
- OSTI ID:
- 22266123
- Journal Information:
- Journal of Applied Physics, Vol. 114, Issue 23; Other Information: (c) 2013 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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