First-Principles Calculation Investigations of Bandgap Bowing Parameters, Electronic and Optical Properties of Cd1 – xZnxTe, Cd1 – xZnxSe and Cd1 – xZnxS Semiconductors Alloys

In this study, we conducted a detailed examination of the energy band gaps in semiconductor alloys, specifically Cd1 – xZnxTe, Cd1 – xZnxSe, and Cd1 – xZnxS, all of which adopt the zinc-blende crystal structure. To carry out our analysis, we used the full-potential linearized augmented plane wave (FP-LAPW) method, applying both the generalized gradient approximation (GGA) and local density approximation (LDA) to achieve accurate results. For precise determination of band gaps and the bowing parameters, we relied on the Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange potential, known for its effectiveness in band structure calculations. Our results showed a moderately nonlinear dependence of band gap values on composition, with bowing parameters estimated at approximately b ≈ 0.49 eV for Cd1 – xZnxTe, b ≈ 0.68 eV for Cd1 – xZnxS, and b ≈ 0.63 eV for Cd1 – xZnxSe. This observed nonlinearity was mainly attributed to volume deformation effects, following the Zunger approach, which explains how structural distortions can impact electronic properties. Beyond band gap analysis, we examined key optical properties, including the absorption coefficient, refractive index, reflectivity, energy loss function, and oscillator strength. These optical characteristics offer deeper insights into the materials' electronic structures and response to light. Interestingly, we observed an increase in the effective electron numbers during photoexcitation as the Zn concentration rose, indicating enhanced optical activity in these alloys. This study sheds light on both electronic and optical properties, making these Cd1 – xZnxTe, Cd1 – xZnxSe, and Cd1 – xZnxS alloys promising candidates for optoelectronic applications where fine-tuning of band gaps and optical responses is essential for optimal device performance.