Highly tensile-strained self-assembled Ge quantum dots on InP substrates for integrated light sources

• Main Authors: Chen, Qimiao, Zhang, Liyao, Song, Yuxin, Chen, Xiren, Koelling, Sebastian, Zhang, Zhenpu, Li, Yaoyao, Koenraad, Paul M., Shao, Jun, Tan, Chuan Seng, Wang, Shumin, Gong, Qian
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Electrical and electronic engineering::Semiconductors; GeSn QD; Mid-IR Light Source
• Online Access: https://hdl.handle.net/10356/146062
• Institution: Nanyang Technological University

Highly tensile-strained Ge quantum dots (TS-Ge-QDs) emitting structures with different size were successfully grown on InP substrates by molecular beam epitaxy. Defect-free samples with TS-Ge-QDs were confirmed 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 bandgap conversion of Ge based on theoretical prediction. Photoluminescence (PL) from a direct bandgap-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 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 bandgap-like transitions of TS-Ge-QDs provides encouraging evidence of this promising method for integrated light source on Si photonics platform.