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Contactless electroreflectance of ZnSe layers grown by atomic layer epitaxy

Robert Kudrawiec 1Jan Misiewicz 1Łukasz Wachnicki 2Elżbieta Guziewicz 2Marek Godlewski 2,3

1. Wrocław University of Technology, Wybrzeże Wyspiańskiego, Wrocław 50-370, Poland
2. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
3. Cardinal Stefan Wyszynski University, College of Science, Warszawa, Poland


ZnSe is a wide band gap II-VI semiconductor which can be easily integrated with GaAs (III-V semiconductor) due to a small lattice mismatch between the two materials. This material can be also quite easily grown by atomic layer deposition (ALD), which is a very cheap growth technique in comparison to molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD) techniques. ALD method provides uniform films with reproducible thickness, low stress and low defect density. Last years we observed a booming interest in this method, since it was applied for deposition of high-k oxides in 45nm generation processors. ALD can be also used for a monocrystalline growth and then is called atomic layer epitaxy (ALE). In this work we studied monocrystalline zinc selenide films grown by ALE. We applied contactless electroreflectance (CER) to study the optical quality of ZnSe layers grown on GaAs and glass substrates. So far CER spectroscopy has never been used to study semiconductor films obtained by ALE. In this measurement technique, instead of measuring the optical reflectance of the material, the derivative with respect to a modulating electric field is evaluated. This approach leads to resonance-like lines in optical spectra at energies corresponding to the singularities in the total optical density of states (TODS). The sharpness of CER resonances is directly associated with the shape of the TODS, i.e. the quality of the material. In the case of ZnSe layers studied in this work, clear CER resonances were observed at the energy of ~2.7 eV. It has been observed that the intensity of these resonances and their broadening depend on the growth conditions and the kind of substrate. In this work obtained CER results will be analyzed in the context of structural investigations for these materials.


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Related papers

Presentation: Poster at E-MRS Fall Meeting 2009, Symposium C, by Robert Kudrawiec
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-23 21:41
Revised:   2009-06-07 00:48