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arXiv 2407.03081physics.opticsphysics.app-ph
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通过分子束外延生长的II型Ge量子点/Si异质结构中的光泵浦太赫兹幅度调制

Optically Pumped Terahertz Amplitude Modulation in Type-II Ge QD/Si heterostructures grown via Molecular Beam Epitaxy

Suprovat Ghosh, Abir Mukherjee, Sudarshan Singh, Samit K Ray, Ananjan Basu, Santanu Manna, Samaresh Das

AI总结:

本文研究MBE生长的Ge量子点/SOI异质结构在太赫兹频段的光泵浦幅度调制,结合NEGF理论模型揭示光生载流子受限对光电导率的调控机制,并在0.1 THz处实现约77%的调制深度提升。

摘要:

本文利用分子束外延(MBE)在绝缘体上硅(SOI)上生长的IV族锗(Ge)量子点(QDs),以探索其在太赫兹(THz)频段的光学行为。在该工作中,由高于带隙的近红外波长泵浦的Ge量子点,在0.1–1.0 THz频率范围内表现出太赫兹幅度调制。外延Ge量子点在太赫兹幅度调制方面优于参考SOI衬底,这归因于与体材料对应物相比,弱受限量子点中产生了更高的载流子。这一点进一步通过基于非平衡格林函数(NEGF)方法的理论模型得到佐证。该模型能够计算光生载流子(PCG)及其在Ge量子点区域中的受限情况。我们的模型还将计算路径从PCG重新导向至相应的等离子体频率,进而得到折射率和太赫兹光电导率。此外,光生受限空穴在Ge量子点-Si界面处的积累在光照后增强,导致太赫兹光电导率下降。太赫兹光电导率的这种增强有助于在0.1 THz处,Ge量子点-Si界面相比裸SOI实现约77%的太赫兹调制深度显著提升。

英文摘要:

This article exploits group-IV germanium (Ge) quantum dots (QDs) on Silicon-on-Insulator (SOI) grown by molecular beam epitaxy (MBE) in order to explore its optical behaviour in the Terahertz (THz) regime. In this work, Ge QDs, pumped by an above bandgap near infrared wavelength, exhibit THz amplitude modulation in the frequency range of 0.1-1.0 THz. The epitaxial Ge QDs outperform reference SOI substrate in THz amplitude modulation owing to higher carrier generation in weakly confined dots compared to its bulk counterpart. This is further corroborated using theoretical model based on the non-equilibrium Green's function (NEGF) method. This model enables the calculation of photo carriers generated (PCG) and their confinement in the Ge QD region. Our model also reroutes the calculation from PCG to corresponding plasma frequency and hence to refractive index and THz photo-conductivity. Moreover, the photo-generated confined holes accumulation at the Ge QDs-Si interface is elevated after optical illumination, leading to a decreased THz photo-conductivity. This augmentation in THz photo-conductivity contributes to a significant enhancement of THz modulation depth ~77% at Ge QDs-Si interfaces compared to bare SOI at 0.1 THz.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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