Layer-dependent electronic, optical, and transport properties of few-layer GeSb 2 Te 4

Abstract Owing to the pronounced contrast between crystalline and amorphous phases, GeSb 2 Te 4 serves as a key phase change memory material. However, existing studies predominantly focuses on bulk or fixed-thickness thin film structures, with limited investigation into the electronic, optical, and transport properties of low-dimensional systems. Using first-principles calculations, we systematically study the evolution of these properties as a function of layer thickness. We find that as the number of layers increases, the band edge shifts toward the Fermi level, leading to the reduction of the band gap from 0.481 eV in monolayer to 0.120 eV in bulk structure. The work function exhibits a decreasing trend with increasing layer number, showing a substantial tunable range of up to 0.4 eV . Monolayer GeSb 2 Te 4 exhibits strong optical absorption, with a peak absorbance exceeding 40% and absorption coefficients on the order of 10 6 cm − 1 in the visible range, and the optical response can be effectively tuned by varying the number of layers. At room temperature, bilayer GeSb 2 Te 4 achieves a total mobility of 30 cm 2 ( V ⋅ s ) − 1 , showing significantly improved carrier transport compared to the monolayer structure. This study elucidates the evolution of key properties of GeSb 2 Te 4 with varying layer thickness and provides theoretical insights for the further optimization of phase-change materials in memory applications.