Thickness-Dependent Optical Properties and Exciton Recombination Dynamics in the GaSe 0.5 Te 0.5 Alloy

High Resolution Image Download MS PowerPoint Slide In this study, we investigate the thickness-dependent optical properties of GaSe 0.5 Te 0.5 alloy by combining Raman spectroscopy, photoluminescence (PL) measurements, and density functional theory (DFT) calculations. Raman measurements reveal thickness-dependent variations in phonon frequencies and intensities below ∼20 nm, enabling thickness identification through frequency differences between phonon modes. In addition, PL measurements show a pronounced quenching of the PL intensity with decreasing thickness, attributed to enhanced nonradiative recombination associated with surface states and thickness-induced modifications of the electronic structure, accompanied by a blueshift of the PL energy. In agreement with these observations, first-principles calculations demonstrate a thickness-driven evolution of the band structure, with a transition from an indirect character in few-layer systems toward a more direct gap in thicker structures, governed by the interplay between quantum confinement and interlayer coupling. Complementary excitation-power-dependent PL measurements further show distinct recombination dynamics in bulk samples, with sublinear behavior for trapped excitons and superlinear dependence for bound and free excitons, consistent with a state-filling mechanism in localized states. These findings establish a consistent framework linking thickness, electronic structure, and recombination processes in GaSe 0.5 Te 0.5 alloy, and provide key insights for the design and optimization of optoelectronic devices based on PTMC alloys.