研究目的
Investigating the optoelectronic properties of Ge1?x?ySixSny/Ge1?xSnx/Ge1?x?ySixSny double heterostructures pseudomorphically grown on a Ge substrate and the formation and characterization of strain-relaxed Ge1?x?ySixSny/Ge1?xSnx/Ge1?x?ySixSny double heterostructures.
研究成果
The study demonstrated the improvement of PL intensity using Ge1?x?ySixSny/Ge1?xSnx/Ge1?x?ySixSny double heterostructures with high energy band offsets and good crystallinity. The PL spectrum at room temperature was deconvoluted into four components originating from direct and indirect bandgap transitions. The formation of strain-relaxed heterostructures was confirmed, but the PL intensity was significantly lower due to poor crystallinity. Post-deposition annealing increased PL intensity by reducing defects.
研究不足
The crystallinity of the Ge1?xSnx layers is influenced by the crystallinity of the underlying Ge1?x?ySixSny layer, which worsens with increasing Si content. The growth temperature of 200°C might be insufficient for high-Si-content Ge1?x?ySixSny layers to achieve preferable crystallinity. The PL intensity of strain-relaxed Ge1?xSnx layers is significantly lower than that of pseudomorphically grown structures due to poor crystallinity.
1：Experimental Design and Method Selection:
The study involved the growth of Ge1?x?ySixSny/Ge1?xSnx/Ge1?x?ySixSny double heterostructures on Ge substrates using molecular beam epitaxy (MBE). The optoelectronic properties were investigated through photoluminescence (PL) measurements.
2：Sample Selection and Data Sources:
P-type Ge(001) wafers were used as substrates. The samples were characterized using Raman spectroscopy, x-ray diffraction two-dimensional reciprocal space mapping (XRD-2DRSM), and in situ reflection high-energy electron diffraction (RHEED).
3：List of Experimental Equipment and Materials:
MBE system, Knudsen cells (K-cell) for Ge and Sn deposition, electron-beam evaporation for Si deposition, YAG laser for PL measurements, cryostat for temperature control, InAs photovoltaic detector for PL detection.
4：Experimental Procedures and Operational Workflow:
The substrates were chemically and thermally cleaned before growth. The growth temperatures for Ge1?x?ySixSny and Ge1?xSnx layers were 200°C and 150°C, respectively. PL measurements were performed at temperatures between 10 K and room temperature.
5：Data Analysis Methods:
The PL spectra were deconvoluted into Gaussian profiles to identify different radiative recombination processes. The temperature dependence of PL intensity and peak positions was analyzed to assign the origins of the components to direct and indirect transitions.
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