期刊
PHYSICAL REVIEW LETTERS
卷 108, 期 2, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.108.027401
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资金
- U.S. Department of Energy, Office of Basic Sciences, Division of Materials Sciences and Engineering, Energy Frontier Research Center for Inverse-Band Design [DE-AC36-08GO28308]
Combining two indirect-gap materials-with different electronic and optical gaps-to create a direct gap material represents an ongoing theoretical challenge with potentially rewarding practical implications, such as optoelectronics integration on a single wafer. We provide an unexpected solution to this classic problem, by spatially melding two indirect-gap materials (Si and Ge) into one strongly dipole-allowed direct-gap material. We leverage a combination of genetic algorithms with a pseudopotential Hamiltonian to search through the astronomic number of variants of Si-n/Ge-m/...=Si-p=Ge-q superstructures grown on (001) Si1-xGex. The search reveals a robust configurational motif-SiGe(2)Si(2)Ge(2)SiGen on (001) SixGe1-x substrate (x <= 0.4) presenting a direct and dipole-allowed gap resulting from an enhanced Gamma-X coupling at the band edges.
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