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Author: Yamamoto, Yuji × End date: 2024 × Start date: 2020 × DDC: 530 × WGL Institute: IHP ×

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Now showing 1 - 4 of 4
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    Non-isothermal phase-field simulations of laser-written in-plane SiGe heterostructures for photonic applications
    (London : Springer Nature, 2021) Aktas, Ozan; Yamamoto, Yuji; Kaynak, Mehmet; Peacock, Anna C.
    Advanced solid-state devices, including lasers and modulators, require semiconductor heterostructures for nanoscale engineering of the electronic bandgap and refractive index. However, existing epitaxial growth methods are limited to fabrication of vertical heterostructures grown layer by layer. Here, we report the use of finite-element-method-based phase-field modelling with thermocapillary convection to investigate laser inscription of in-plane heterostructures within silicon-germanium films. The modelling is supported by experimental work using epitaxially-grown Si0.5Ge0.5 layers. The phase-field simulations reveal that various in-plane heterostructures with single or periodic interfaces can be fabricated by controlling phase segregation through modulation of the scan speed, power, and beam position. Optical simulations are used to demonstrate the potential for two devices: graded-index waveguides with Ge-rich (>70%) cores, and waveguide Bragg gratings with nanoscale periods (100–500 nm). Periodic heterostructure formation via sub-millisecond modulation of the laser parameters opens a route for post-growth fabrication of in-plane quantum wells and superlattices in semiconductor alloy films.
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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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    Heteroepitaxy of group IV materials for future device application
    (Bristol : IOP Publ., 2023) Yamamoto, Yuji; Wen, Wei-Chen; Tillack, Bernd
    Heteroepitxy of group IV materials (Si, SiGe, and Ge) has great potential for boosting Si-based novel device performance because of the possibility for strain, band gap/Fermi-level engineering, and applying emerging artificial materials such as a superlattice (SL) and nanodots. In order to control group IV heteroepitaxy processes, strain, interface, and surface energies are very essential parameters. They affect dislocation formation, interface steepness, reflow of deposited layers, and also surface reaction itself during the growth. Therefore, process control and crystallinity management of SiGe heteroepitaxy are difficult especially in the case of high Ge concentrations. In this paper, we review our results of abrupt SiGe/Si interface fabrication by introducing C-delta layers and the influence of strain on the surface reaction of SiGe. Three-dimensional self-ordered SiGe and Ge nanodot fabrication by proactively using strain and surface energies by depositing SiGe/Si and Ge/SiGe SL are also reviewed.
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    Vertical alignment control of self-ordered multilayered Ge nanodots on SiGe
    (Bristol : IOP Publ., 2023) Wen, Wei-Chen; Schubert, Markus Andreas; Tillack, Bernd; Yamamoto, Yuji
    Self-ordered multilayered Ge nanodots with SiGe spacers on a Si0.4Ge0.6 virtual substrate are fabricated using reduced-pressure chemical vapor deposition, and the mechanism of vertical ordering is investigated. The process conditions of Ge and SiGe layer deposition are H2-GeH4 at 550 °C and H2-SiH4-GeH4 at 500 °C-550 °C, respectively. By depositing the SiGe at 550 °C or increasing Ge content, the SiGe surface becomes smooth, resulting in vertically aligned Ge nanodots to reduce strain energy. Ge nanodots prefer to grow on the nanodot where the SiGe is relatively tensile strained due to the buried Ge nanodot underneath. By depositing at 500 °C and lowering Ge content, checkerboard-like surface forms, and the following Ge nanodots grow at staggered positions to reduce surface energy. The Ge nanodots are laterally aligned along the elastically soft 〈100〉 direction without pre-structuring resulting from the strain distribution.