Pressure-tuned structural, electronic, optical and phonon properties of ZnTe in zinc-blende (B3) phase

Abstract

High-pressure engineering provides an effective approach for tuning the electronic and optical properties of semiconductors. The density functional theory (DFT) and density functional perturbation theory (DFPT) have been employed to investigate the pressure-dependent structural, electronic, optical and vibrational properties of zinc-blende ZnTe (B3 phase) over the pressure range, 0-20 GPa. The electronic structure is analyzed using the Perdew-Burke-Ernzerhof (PBE) functional, while hybrid HSE06 functional is adopted to improve the band-gap prediction. The influence of spin-orbit coupling (SOC) on the electronic band structure has been examined. At ambient pressure, ZnTe exhibits a direct bandgap, Γ-Γ. HSE06 has predicted a bandgap, 2.63 eV, in agreement with experimental work, whereas PBE underestimates it (1.083 eV). SOC reduces the energy bandgap through the splitting of valence-band states Te-5p without altering its direct-gap character. Under compression, the bandgap decreases continuously and undergoes a direct-to-indirect transition at 18 GPa. The optical spectra reveal significant pressure-induced changes in the dielectric response, particularly an enhanced and tunable reflectivity in the far-ultraviolet region. Phonon calculations further indicate a gradual softening of vibrational modes with an increased pressure, suggesting the onset of dynamical instability before the electronic transition. These findings provide a comprehensive understanding of interplay between the pressure and relativistic effects in ZnTe and demonstrate its potential for pressure-tunable ultraviolet optoelectronic and photonic applications.