Filters

2020 - 20232

More filters

2021 - 20232
Reset filters

Settings

End date: 2024 × DDC: 530 × Publisher: College Park, Md. [u.a.] : American Physical Society × WGL Institute: IHP ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    Role of Oxygen Defects in Conductive-Filament Formation in Y2O3-Based Analog RRAM Devices as Revealed by Fluctuation Spectroscopy
    (College Park, Md. [u.a.] : American Physical Society, 2020) Piros, Eszter; Lonsky, Martin; Petzold, Stefan; Zintler, Alexander; Sharath, S.U.; Vogel, Tobias; Kaiser, Nico; Eilhardt, Robert; Molina-Luna, Leopoldo; Wenger, Christian; Müller, Jens; Alff, Lambert
    Low-frequency noise in Y2O3-based resistive random-access memory devices with analog switching is studied at intermediate resistive states and as a function of dc cycling. A universal 1/fα-type behavior is found, with a frequency exponent of α≈1.2 that is independent of the applied reset voltage or the device resistance and is attributed to the intrinsic abundance of oxygen vacancies unique to the structure of yttria. Remarkably, the noise magnitude in the high resistive state systematically decreases through dc training. This effect is attributed to the stabilization of the conductive filament via the consumption of oxygen vacancies, thus reducing the number of active fluctuators in the vicinity of the filament.