Optical properties and structural characteristics of ZnMgO grown by plasma assisted molecular beam epitaxy

Wurtzite Zn 1 − x Mg x O thin films with Mg contents between x = 0 and x = 0.37 were grown on c -plane sapphire substrates by plasma assisted molecular beam epitaxy using a MgO/ZnMgO buffer layer. The a -lattice parameter is independent from the Mg concentration, whereas the c -lattice parameter dec...

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Bibliographic Details
Published in:Journal of applied physics 2009-01, Vol.105 (2), p.023505-023505-6
Main Authors: Wassner, Thomas A., Laumer, Bernhard, Maier, Stefan, Laufer, Andreas, Meyer, Bruno K., Stutzmann, Martin, Eickhoff, Martin
Format: Article
Language:English
Subjects:
ALLOYS
EV RANGE 01-10
EXCITONS
LATTICE PARAMETERS
LAYERS
MAGNESIUM OXIDES
MATERIALS SCIENCE
MOLECULAR BEAM EPITAXY
OPTICAL PROPERTIES
PHOTOLUMINESCENCE
PLASMA
SAPPHIRE
SEMICONDUCTOR MATERIALS
SPECTRAL SHIFT
SUBSTRATES
THIN FILMS
ZINC COMPOUNDS
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Summary:Wurtzite Zn 1 − x Mg x O thin films with Mg contents between x = 0 and x = 0.37 were grown on c -plane sapphire substrates by plasma assisted molecular beam epitaxy using a MgO/ZnMgO buffer layer. The a -lattice parameter is independent from the Mg concentration, whereas the c -lattice parameter decreases from 5.20 Å for x = 0 to 5.17 Å for x = 0.37 , indicating pseudomorphic growth. The near band edge photoluminescence shows a blueshift with increasing Mg concentration to an emission energy of 4.11 eV for x = 0.37 . Simultaneously, the energetic position of the deep defect luminescence shows a linear shift from 2.2 to 2.8 eV. Low temperature transmission measurements reveal strong excitonic features for the investigated composition range and alloy broadening effects for higher Mg contents. The Stokes shift as well as the Urbach energy is increased to values of up to 125 and 54 meV for x = 0.37 , respectively, indicating exciton localization due to alloy fluctuations.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3065535