Ge{sub 1-y}Sn{sub y} (y = 0.01-0.10) alloys on Ge-buffered Si: Synthesis, microstructure, and optical properties
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)
- Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)
- LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287-1704 (United States)
Novel hydride chemistries are employed to deposit light-emitting Ge{sub 1-y}Sn{sub y} alloys with y ≤ 0.1 by Ultra-High Vacuum Chemical Vapor Deposition (UHV-CVD) on Ge-buffered Si wafers. The properties of the resultant materials are systematically compared with similar alloys grown directly on Si wafers. The fundamental difference between the two systems is a fivefold (and higher) decrease in lattice mismatch between film and virtual substrate, allowing direct integration of bulk-like crystals with planar surfaces and relatively low dislocation densities. For y ≤ 0.06, the CVD precursors used were digermane Ge₂H₆ and deuterated stannane SnD₄. For y ≥ 0.06, the Ge precursor was changed to trigermane Ge₃H₈, whose higher reactivity enabled the fabrication of supersaturated samples with the target film parameters. In all cases, the Ge wafers were produced using tetragermane Ge₄H₁₀ as the Ge source. The photoluminescence intensity from Ge{sub 1–y}Sn{sub y}/Ge films is expected to increase relative to Ge{sub 1–y}Sn{sub y}/Si due to the less defected interface with the virtual substrate. However, while Ge{sub 1–y}Sn{sub y}/Si films are largely relaxed, a significant amount of compressive strain may be present in the Ge{sub 1–y}Sn{sub y}/Ge case. This compressive strain can reduce the emission intensity by increasing the separation between the direct and indirect edges. In this context, it is shown here that the proposed CVD approach to Ge{sub 1–y}Sn{sub y}/Ge makes it possible to approach film thicknesses of about 1 μm, for which the strain is mostly relaxed and the photoluminescence intensity increases by one order of magnitude relative to Ge{sub 1–y}Sn{sub y}/Si films. The observed strain relaxation is shown to be consistent with predictions from strain-relaxation models first developed for the Si{sub 1–x}Ge{sub x}/Si system. The defect structure and atomic distributions in the films are studied in detail using advanced electron-microscopy techniques, including aberration corrected STEM imaging and EELS mapping of the average diamond–cubic lattice.
- OSTI ID:
- 22305744
- Journal Information:
- Journal of Applied Physics, Vol. 116, Issue 13; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
BUFFERS
CHEMICAL VAPOR DEPOSITION
CRYSTAL DEFECTS
CRYSTALS
CUBIC LATTICES
DISLOCATIONS
ELECTRON MICROSCOPY
FILMS
GERMANIUM COMPOUNDS
GERMANIUM HYDRIDES
LIGHT EMITTING DIODES
MICROSTRUCTURE
OPTICAL PROPERTIES
PHOTOLUMINESCENCE
RELAXATION
SILICON
SUBSTRATES
THICKNESS
TIN COMPOUNDS