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GeSn合金作为一种新型硅基光电材料，因其带隙可调特性以及兼容硅基CMOS工艺等优点，在红外光子学领域展现出显著的应用潜力。尽管GeSn激光器在低温条件下的实验性能已得到初步验证，但该器件的优化与实际应用仍面临着对材料特性的认识尚不充分等挑战。本文针对GeSn合金在红外光子学应用中存在的载流子动力学机制不明等问题，通过建立包含能带参数、非平衡态载流子输运和辐射复合的唯象理论模型，系统研究了变温条件下热激发和声子辅助过程对GeSn合金直接带自发发射影响的机理。研究结果表明，GeSn合金ΓCBM与LCBM能谷间的载流子转移过程表现出显著的组分依赖性：对于Sn组分小于10%的低组分GeSn合金，温度诱导的LCBM→ΓCBM电子转移占主导，导致直接带发光效率随着温度的升高而增强；而在Sn组分在10%-20%的高组分GeSn合金中，ΓCBM→LCBM的电子逃逸过程更为显著，造成直接带发光效率随着温度的升高而降低。改进型Arrhenius模型分析载流子谷间输运与辐射复合的竞争机制进一步表明，热激发和声子辅助对ΓCBM能谷电子注入或者逃逸均有促进作用，是提升或者降低GeSn合金直接带隙辐射复合效率的关键因素。GeSn合金自发发射谱的峰位红移主要源于带隙收缩效应；同时声子辅助过程会降低载流子能量分布的离散性，导致直接带发射谱谱线窄化效应明显。量化研究结果进一步揭示了GeSn合金中载流子的热激发和声子辅助对直接带隙发光影响的机制，可为其在红外光电器件中的性能调控提供理论参考。GeSn alloy, as a novel silicon-based optoelectronic material, demonstrates significant application potential in the field of infrared photonics due to its tunable bandgap properties and compatibility with silicon-based CMOS processes. Although the experimental performance of GeSn lasers under low-temperature conditions has been preliminarily validated, the optimization and practical application of this device still face challenges such as insufficient understanding of material properties. This paper addresses issues such as the unclear carrier dynamics mechanisms in GeSn alloy applications in infrared photonics. A theoretical model incorporating band parameters, non-equilibrium carrier transport, and radiative recombination have been proposed to systematically investigate the mechanism by which thermal excitation and phonon-assisted processes influence the direct-band spontaneous emission in GeSn alloys under variable temperature conditions. Results indicate that the carrier transfer process between the ΓCBM and LCBM energy bands of GeSn alloys exhibits significant composition dependence: for low-Sn-content GeSn alloys with Sn content below 10%, temperature-induced LCBM→ΓCBM electron transfer dominates, leading to an increase in direct band emission efficiency with rising temperature; whereas in high-Sn-content GeSn alloys with Sn content between 10% and 20%, the ΓCBM→LCBM electron escape process is more pronounced, resulting in a decrease in direct band emission efficiency with rising temperature. A modified Arrhenius modeling of the carrier dynamics competition further indicates that thermal excitation and phonon scattering synergistically regulate electron transfer between ΓCBM and LCBM. Analysis based on the modified Arrhenius model further demonstrates that both thermal excitation and phonon-assisted processes promote the injection and escape of electrons in the ΓCBM valley, serving as key factors in modulating the radiative recombination efficiency at the direct bandgap of GeSn alloys. The red shift of the peak position in the spontaneous emission spectrum of GeSn alloys primarily originates from the bandgap contraction effect; simultaneously, phonon-assisted processes reduce the dispersion of carrier energy distributions, leading to a pronounced narrowing effect in the direct band emission spectrum. Quantitative findings further elucidate the mechanism by which thermal excitation and phonon-assisted processes influence direct bandgap luminescence in GeSn alloys, offering theoretical guidance for performance regulation in infrared optoelectronic devices.
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Keywords:
- GeSn alloys /
- Thermal excitation /
- Phonon assisted /
- Direct band emission
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