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  1. The incorporation of dilute concentrations of bismuth into traditional III–V alloys produces significant reductions in bandgap energy presenting unique opportunities in strain and bandgap engineering. However, the disparity between the ideal growth conditions for the host matrix and those required for substitutional bismuth incorporation has caused the material quality of these III–V–Bi alloys to lag behind that of conventional III–V semiconductors. InSb1−xBix, while experimentally underexplored, is a promising candidate for high-quality III–V–Bi alloys due to the relatively similar ideal growth temperatures for InSb and III–Bi materials. By identifying a highly kinetically limited growth regime, we demonstrate the growth of high-quality InSb1−xBix by molecular beam epitaxy. X-ray diffraction and Rutherford backscattering spectrometry (RBS) measurements of the alloy's bismuth concentration, coupled with smooth surface morphologies as measured by atomic force microscopy, suggest unity-sticking bismuth incorporation for a range of bismuth concentrations from 0.8% to 1.5% as measured by RBS. In addition, the first photoluminescence was observed from InSb1−xBix and demonstrated wavelength extension up to 7.6 μm at 230 K, with a bismuth-induced bandgap reduction of ∼29 meV/% Bi. Furthermore, we report the temperature dependence of the bandgap of InSb1−xBix and observed behavior consistent with that of a traditional III–V alloy. The results presented highlight the potential of InSb1−xBix as an alternative emerging candidate for accessing the longwave-infrared.

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  5. In integrated photonics, specific wavelengths such as 1,550 nm are preferred due to low-loss transmission and the availability of optical gain in this spectral region. For chip-based photodetectors, two-dimensional materials bear scientifically and technologically relevant properties such as electrostatic tunability and strong light–matter interactions. However, no efficient photodetector in the telecommunication C-band has been realized with two-dimensional transition metal dichalcogenide materials due to their large optical bandgaps. Here we demonstrate a MoTe2-based photodetector featuring a strong photoresponse (responsivity 0.5 A W–1) operating at 1,550 nm in silicon photonics enabled by strain engineering the two-dimensional material. Non-planarized waveguide structures show a bandgap modulation of 0.2 eV, resulting in a large photoresponse in an otherwise photoinactive medium when unstrained. Unlike graphene-based photodetectors that rely on a gapless band structure, this photodetector shows an approximately 100-fold reduction in dark current, enabling an efficient noise-equivalent power of 90 pW Hz–0.5. Such a strain-engineered integrated photodetector provides new opportunities for integrated optoelectronic systems. 
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