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Lattice parameters of a wurtzite-type (Zn,Mg)Se crystal as a function of temperature
|Wojciech Paszkowicz 1, Paweł Piszora 2, Franciszek S. Firszt 3, Hanna Męczyńska 3, Stanisław Łęgowski 3, Carsten Baehtz 4, Michael Knapp 5|
1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
Wide gap II-VI semiconductors exhibit properties leading to various possible applications in optoelectronics. Structural and elastic properties of these materials are thus of high importance. (Zn,Mg)Se and related materials are studied since 1983 when their applications were suggested [1,2,3]. Most of considered applicatiions concern the alloys of low or moderate Mg content. Components with high-Mg-content can be used e.g. for control elements for IR optics . Thin-film engineering involves tuning the lattice-parameter and bandgap values. The tuning is performed through selection of the given solid-solution composition, taking into account the need for lattice matching and required bandgap. Learning the structural and physical properties of the solution isa first step to design of layers and multilayers of desired characteristics. The opportunity of preparation of the solution as a single phase depends on the system and on the crystallisation process and its parameters. For the (Zn,Mg)Se system, the solid solution can be prepared in a broad range of Mg concentration, but the structure has been found to be different for bulk crystals than for epitaxial layers deposited on GaAs or InP. Alloying ZnSe with MgSe provides a way of tuning the ZnSe properties, in particular, its lattice parameters and bandgap increase with rising Mg content. Knowledge of bulk-crystal thermal expansivity is of importance for construction of optoelectronic devices, involving the (Zn,Mg)Se layers as building blocks. In this study, a wurtzite type (Zn,Mg)Se crystal grown by the high-pressure Bridgman method is studied by X-ray diffraction in the 10-290 K temperature range. The temperature variations of lattice parameter and thermal expansion coefficients are determined. An increase of thermal expansion coefficient with Mg content is observed.
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Presentation: Poster at 11th European Powder Diffraction Conference, Poster session, by Wojciech Paszkowicz
See On-line Journal of 11th European Powder Diffraction Conference
Submitted: 2008-07-25 01:14 Revised: 2009-06-07 00:48