Tyndall National Institute - Conference Items
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Item Efficient quantum simulations of devices based on 2D materials including vertical heterojunctions(Institute of Electrical and Electronics Engineers (IEEE), 2024-10-31) Sanchez-Soares, Alfonso; Kelly, T.; Su, S.-K.; Chen, E.; Greer, James C.; Fagas, GeorgiosWe present a modelling framework that enables efficient exploration of the electrical performance of devices based on 2D material vertical heterojunctions. Electronic structure data from density functional theory (DFT) simulations is used to extract parameters for k.p Hamiltonians. Material models are then employed in device simulations based on non-equilibrium Green's functions (NEGF) for a quantum-mechanical description of charge transport. Electron-phonon scattering is included in order to account for dissipative phenomena as well as phonon-assisted interlayer charge transport. We demonstrate our methodology with an application to a Dirac-source field-effect transistor (DS-FET) design based on a monolayer molybdenum disulfide channel (ML-MoS2) with a graphene contact.Item Establishing composition dependent k · p parameters for (Al,Ga)N alloys(Institute of Electrical and Electronics Engineers (IEEE), 2024-10-23) Singh, Amit Kumar; Gomez-Iglesias, Alvaro; Schulz, Stefan; Horizon 2020; Science Foundation IrelandDeep UV (Al,Ga)N-based light emitters exhibit very low quantum efficiencies when compared to UV emitters at longer wavelengths. To improve the efficiencies of e.g. (Al,Ga)N-based light emitting diodes, theory and simulation can help to guide the device design. The theoretical framework underlying device simulations is often based on drift-diffusion models coupled with a self-consistent Schrodinger-Poisson equation solver. To achieve accurate and predictive models, understanding the composition dependence of material input parameters is of central importance. We target the composition dependence of k⋅p parameters in AlxGa(1−x)N alloys by using density functional theory (DFT) to obtain effective band structures from alloy disordered supercells. Building on these effective band structures, a numerically efficient fitting scheme based on the Sobol-sequence method is employed to extract effective electron masses, me(x) , Luttinger-like parameters Ai(x) , with i=1…6 , and crystal field splitting energy, ΔCF , as a function of Al content, x , in the system. Our calculations reveal that for me(x) a linear interpolation of the GaN and AlN values provides a good description of the DFT data. However, for Ai(x) and ΔCF(x) this simple approximation breaks down and we find that composition dependent bowing parameters are required to describe effective DFT band structures accurately.Item Low-complexity frequency packing to enable filtering-tolerant DSCM transmission(Optica Publishing Group, 2024) Patel, Romil K.; Mumtaz, Sami; Fernandes, Marco A.; Oliveira, Beatriz M.; Charlet, Gabriel; Zhao, Yu; Monteiro, Paulo P.; Lorences-Riesgo, Abel; Guiomar, Fernando P.; Fundação para a Ciência e a Tecnologia; Horizon 2020; Tyndall National InstituteEmploying optimized frequency packing over digital subcarrier multiplexing (DSCM), we exploit the mitigation of WSS filtering penalties. After transmitting a 60 Gbaud 8-DSCM with 0.2 roll-off over 5-10 WSSs, we experimentally demonstrate OSNR gains of >3 dB, without additional DSP complexity.Item FPGA-programmable 512 Gbps 2.5D DWDM photonic network interface card(Optica Publishing Group, 2024-10-29) Robinson, James; Hattink, Maarten; Dai, Liang Yuan; Haimowitz, Max; Li, Mao; Jang, Daniel; Morrissey, Padraic; Malik, Arun Kumar; O’Brien, Peter; Robertson, Seth; Seok, Mingoo; Bergman, Keren; Defense Advanced Research Projects Agency; U.S. Department of EnergyWe present a 2.5D integrated, FPGA-programmable silicon photonic network interface card implementing a bidirectional 512Gbps dense wavelength-division multiplexed link. We demonstrate sixteen transmitter and eight of sixteen receiver channels operating error-free at 16 Gbps each.Item Endoscopic photon time-of-flight system for monitoring chemotherapy response(Optica Publishing Group, 2024) Yavari, Hasti; Kothuri, Suraj Kumar; Lanka, Pranav; Andersson-Engels, Stefan; Sekar, Sanathana Konugolu Venkata; Science Foundation IrelandWe present a hybrid micro-camera time of flight endoscopy system to assess tumor response both superficially and deep below the mucosa layer. System design and preliminary results are presented.