Electronic structure of lonsdaleite SixGe1−x alloys

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Broderick, Christopher A.
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Institute of Electrical and Electronics Engineers (IEEE)
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Conventional diamond-structured silicon (Si) and germanium (Ge) possess indirect fundamental band gaps, limiting their potential for applications in light-emitting devices. However, SixGe1-x alloys grown in the lonsdaleite ("hexagonal diamond") phase have recently emerged as a promising directgap, Si-compatible material system, with experimental measurements demonstrating strong room temperature photoluminescence. When grown in the lonsdaleite phase, Ge possesses a narrow (0:3 eV) "pseudo-direct"fundamental band gap. Lonsdaleite Si is indirect-gap (0:8 eV), creating the possibility to achieve direct-gap lonsdaleite SixGe1-x alloys across a Gerich composition range. We present a first principles analysis of the electronic and optical properties of lonsdaleite SixGe1-x alloys, elucidate the electronic structure evolution and direct-to indirect-gap transition, and describe the impact of alloy band mixing effects on inter-band optical transition strengths.
Electronic , Optical , lonsdaleite SixGe1-x alloys , Ab initio calculations , Energy gap , Ge-Si alloys , Optical constants , Photoluminescence
Broderick, C. A. (2020) 'Electronic structure of lonsdaleite SixGe1-x alloys', Proceedings of the International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), Turin, Italy, 14-18 September, pp. 3-4. doi: 10.1109/NUSOD49422.2020.9217637
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