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Highly Tensile-Strained Self-Assembled Ge Quantum Dots on InP Substrates for Integrated Light Sources

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journal contribution
posted on 06.01.2021, 18:17 by Qimiao Chen, Liyao Zhang, Yuxin Song, Xiren Chen, Sebastian Koelling, Zhenpu Zhang, Yaoyao Li, Paul M. Koenraad, Jun Shao, Chuan Seng Tan, Shumin Wang, Qian Gong
Highly tensile-strained Ge quantum dots (TS-Ge-QDs) emitting structures with different size were successfully grown on InP substrates by molecular beam epitaxy. Dislocation-free TS-Ge-QDs were observed by transmission electron microscopy. Finite element modeling indicates a maximum tensile strain of 4.5% in the Ge QDs, which is much larger than the required strain to achieve direct band gap conversion of Ge based on theoretical prediction. Photoluminescence (PL) from a direct band-gap-like transition of TS-Ge-QDs with a peak energy of 0.796 eV was achieved and confirmed by the etch depth-dependent PL, temperature-dependent PL, and excitation-power-dependent PL. In addition, a strong defect-related peak of 1 eV was observed at room temperature. The band structure of the TS-Ge-QDs emitting structures was calculated to support the experimental results of PL spectra. Achieving PL from direct band-gap-like transitions of TS-Ge-QDs provides encouraging evidence of this promising highly tensile strained semiconductor-nanostructure-based platform for future photonics applications such as integrated light sources.

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