Browsing by Author "Talamas Simola, Enrico"

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    CMOS-Compatible Bias-Tunable Dual-Band Detector Based on GeSn/Ge/Si Coupled Photodiodes
    (Washington, DC : ACS Publications, 2021) Talamas Simola, Enrico; Kiyek, Vivien; Ballabio, Andrea; Schlykow, Viktoria; Frigerio, Jacopo; Zucchetti, Carlo; De Iacovo, Andrea; Colace, Lorenzo; Yamamoto, Yuji; Capellini, Giovanni; Grützmacher, Detlev; Buca, Dan; Isella, Giovanni
    Infrared (IR) multispectral detection is attracting increasing interest with the rising demand for high spectral sensitivity, room temperature operation, CMOS-compatible devices. Here, we present a two-terminal dual-band detector, which provides a bias-switchable spectral response in two distinct IR bands. The device is obtained from a vertical GeSn/Ge/Si stack, forming a double junction n-i-p-i-n structure, epitaxially grown on a Si wafer. The photoresponse can be switched by inverting the bias polarity between the near and the short-wave IR bands, with specific detectivities of 1.9 × 1010 and 4.0 × 109 cm·(Hz)1/2/W, respectively. The possibility of detecting two spectral bands with the same pixel opens up interesting applications in the field of IR imaging and material recognition, as shown in a solvent detection test. The continuous voltage tuning, combined with the nonlinear photoresponse of the detector, enables a novel approach to spectral analysis, demonstrated by identifying the wavelength of a monochromatic beam. © 2021 The Authors. Published by American Chemical Society.
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    Subnanometer Control of the Heteroepitaxial Growth of Multimicrometer-Thick Ge /(Si, Ge) Quantum Cascade Structures
    (College Park, Md. [u.a.] : American Physical Society, 2023) Talamas Simola, Enrico; Montanari, Michele; Corley-Wiciak, Cedric; Di Gaspare, Luciana; Persichetti, Luca; Zöllner, Marvin H.; Schubert, Markus A.; Venanzi, Tommaso; Trouche, Marina Cagnon; Ortolani, Michele; Mattioli, Francesco; Sfuncia, Gianfranco; Nicotra, Giuseppe; Capellini, Giovanni; Virgilio, Michele; De Seta, Monica
    The fabrication of complex low-dimensional quantum devices requires the control of the heteroepitaxial growth at the subnanometer scale. This is particularly challenging when the total thickness of stacked layers of device-active material becomes extremely large and exceeds the multi-μm limit, as in the case of quantum cascade structures. Here, we use the ultrahigh-vacuum chemical vapor deposition technique for the growth of multi-μm-thick stacks of high Ge content strain-balanced Ge/SiGe tunneling heterostructures on Si substrates, designed to serve as the active material in a THz quantum cascade laser. By combining thorough structural investigation with THz spectroscopy absorption experiments and numerical simulations we show that the optimized deposition process can produce state-of-the-art threading dislocation density, ultrasharp interfaces, control of dopant atom position at the nanoscale, and reproducibility within 1% of the layer thickness and composition within the whole multilayer. We show that by using ultrahigh-vacuum chemical vapor deposition one achieves simultaneously a control of the epitaxy down to the sub-nm scale typical of the molecular beam epitaxy, and the high growth rate and technological relevance of chemical vapor deposition. Thus, this technique is a key enabler for the deposition of integrated THz devices and other complex quantum structures based on the Ge/SiGe material system.