Effects of in-plane tensile strains on structural, electronic, and optical properties of CdSe

• In-plane strain induced structural transformation for wurtzite CdSe at strain of 9.3%.
• Electronic energy band gap transition from direct to indirect was found when applying strain larger than 9.3%.
• A comparison study between the optical properties of unstrained and strained CdSe was investigated.
• A considerable anisotropy was found for CdSe under large in-plane strain.

First-principles density functional theory was used to investigate effects of in-plane strains on the structural, electronic, and optical properties of wurtzite cadmium selenide (CdSe). The results of this work show some interesting properties of this material under finite strains that do not exist in the bulk unstrained regime. The structural deformation produced by increasing the in-plane strain, including the internal parameter u, was examined. The result shows that the structure undergoes a phase transition at a strain of 9.3% due to an extraordinary increase of the internal parameter u. By analyzing the electronic band structure using the modified Becke–Johnson approximation (mBJ), a direct–indirect band gap transition at an in-plane strain of 9.3% was found. Additionally, optical dielectric constants, reflectivity, and refractive index were calculated at different values of the strain. These results indicate that, by controlling the CdSe biaxial in-plane lattice constant (for example, by epitaxial growth on an appropriate substrate), the electronic and optical properties can be tuned for specific device applications.

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