Lin Pin-Hao, Ghosh Soumava, Chang Guo-En
Department of Mechanical Engineering, and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chiayi 621301, Taiwan.
Sensors (Basel). 2024 Feb 16;24(4):1263. doi: 10.3390/s24041263.
GeSn alloys have recently emerged as complementary metal-oxide-semiconductor (CMOS)-compatible materials for optoelectronic applications. Although various photonic devices based on GeSn thin films have been developed, low-dimensional GeSn quantum structures with improved efficiencies hold great promise for optoelectronic applications. This study theoretically analyses Ge-capped GeSn pyramid quantum dots (QDs) on Ge substrates to explore their potential for such applications. Theoretical models are presented to calculate the effects of the Sn content and the sizes of the GeSn QDs on the strain distributions caused by lattice mismatch, the band structures, transition energies, wavefunctions of confined electrons and holes, and transition probabilities. The bandgap energies of the GeSn QDs decrease with the increasing Sn content, leading to higher band offsets and improved carrier confinement, in addition to electron-hole wavefunction overlap. The GeSn QDs on the Ge substrate provide crucial type-I alignment, but with a limited band offset, thereby decreasing carrier confinement. However, the GeSn QDs on the Ge substrate show a direct bandgap at higher Sn compositions and exhibit a ground-state transition energy of ~0.8 eV, rendering this system suitable for applications in the telecommunication window (1550 nm). These results provide important insights into the practical feasibility of GeSn QD systems for optoelectronic applications.
锗锡合金最近已成为用于光电子应用的与互补金属氧化物半导体（CMOS）兼容的材料。尽管已经开发了各种基于锗锡薄膜的光子器件，但具有更高效率的低维锗锡量子结构在光电子应用中具有巨大潜力。本研究从理论上分析了锗衬底上的锗帽锗锡金字塔量子点（QD），以探索其在此类应用中的潜力。提出了理论模型来计算锡含量和锗锡量子点尺寸对由晶格失配引起的应变分布、能带结构、跃迁能量、受限电子和空穴的波函数以及跃迁概率的影响。锗锡量子点的带隙能量随着锡含量的增加而降低，除了电子 - 空穴波函数重叠外，还导致更高的带偏移和改善的载流子限制。锗衬底上的锗锡量子点提供了关键的I型对准，但带偏移有限，从而降低了载流子限制。然而，锗衬底上的锗锡量子点在较高锡组成时表现出直接带隙，并表现出约0.8 eV的基态跃迁能量，使得该系统适用于电信窗口（1550 nm）中的应用。这些结果为锗锡量子点系统在光电子应用中的实际可行性提供了重要见解。
