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This study aims to explore two-dimensional semiconductor materials with superior carrier transport properties to meet the growing demands of high-speed electronics and optoelectronic devices, focusing on evaluating the feasibility of monolayer FeGa2S4 as a candidate material through systematic theoretical investigations. First-principles calculations are used to analyze the exfoliation energy of FeGa2S4 bulk crystal, as well as the structural stability, mechanical properties, and strain-dependent optoelectronic behavior of its monolayer counterpart. Strain engineering strategies, including uniaxial and biaxial strain, are used to assess carrier mobility modulation and spectral response. Our calculation results indicate that monolayer FeGa2S4 is an indirect bandgap semiconductor (Eg = 1.65 eV) with low stiffness (Young’s modulus up to 151.6 GPa) and high flexibility (Poisson’s ratio less than 0.25), demonstrating exceptional thermodynamic stability. Under +5% uniaxial tensile strain, its electron mobilities along x and y directions dramatically increases to 5402.4 cm2·V–1·s–1 and 4164.0 cm2·V–1·s–1, fivefold higher than its hole mobility. Biaxial strain outperforms uniaxial strain in bandgap modulation and induces a systematic redshift in optical spectra, significantly enhancing visible-light harvesting efficiency. This work reveals that monolayer FeGa2S4 is a promising high-mobility photoactive material for next-generation solar cells and optoelectronics. The strain-mediated control of electronic and optical properties provides a theoretical framework for optimizing 2D semiconductors and critical guidance for experimental synthesis and device engineering. These findings highlight the potential of materials in advancing energy conversion technology and photonic applications.
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Keywords:
- first-principles /
- electronic structure /
- optical properties /
- strain engineering
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图 1 (a) 体相FeGa2S4晶体结构的侧视图, 黑框内为其块材的一个原胞; (b) FeGa2S4的剥离能
Figure 1. (a) Side view of FeGa2S4 bulk, its primitive cell is marked with a black frame; (b) the exfoliation energy of FeGa2S4
图 2 单层FeGa2S4的结构示意图 (a) 俯视图; (b) 侧视图; (c) 单胞的声子谱; (d) 3×3×1超晶胞结构分子动力学模拟
Figure 2. (a) Top and (b) side views of FeGa2S4 monolayer, (c) phonon dispersion curves of FeGa2S4 monolayer unit cell; (d) evolution of total energy and snapshots of FeGa2S4 monolayer 3×3×1 supercell from AIMD simulations.
图 3 FeGa2S4单层面内杨氏模量(a)和泊松比(b)
Figure 3. Young’s moduli (a) and Poisson’s ratio (b) of FeGa2S4 monolayer.
图 4 FeGa2S4单层的电子能带结构和分波态密度
Figure 4. Band structure and PDOS of monolayer FeGa2S4.
图 5 (a) x和y输运方向的定义; (b) 单层FeGa2S4的载流子迁移率应变响应特性
Figure 5. (a) Definition of transport directions x and y; (b) carrier mobility of monolayer FeGa2S4 under uniaxial strain.
图 6 单层FeGa2S4超胞的导带底局域电荷密度示意图及轨道投影能带图
Figure 6. Partial charge densities of the conduction band minimum and projected band structure of FeGa2S4 monolayer supercell.
图 7 单层FeGa2S4带隙随面内单双轴应变变化曲线
Figure 7. Variation of band gap of FeGa2S4 monolayer with various in-plane strain.
图 8 双轴应变ε = 0%, ε = ±3%和ε = +5%时, 单层FeGa2S4的吸收率、反射率和透射率
Figure 8. Absorption, reflectance and transmission of monolayer FeGa2S4 under ε = 0%, ε = ±3% and ε = +5% biaxial strain.
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