1,721,030 research outputs found
Investigation of Static and Dynamic Characteristics of Optically Controlled Field Effect Transistors
No full textIn this paper, we report on an optically controlled field effect transistor (OCFET). The device is based on a modified MOSFET geometry with a Germanium layer interposed between the gate oxide and the gate metal contact. The investigation is performed using the technology computer aided design tool. We describe the principle of operation and investigate the static and dynamic properties of the OCFET under near infrared light at 1.55 mu m. Device performance in terms of both ON/OFF current ratio and switching times are studied versus design parameters such as Germanium doping and lifetime as well as gate bias voltage and optical power. Strategies toward best operating conditions and satisfactory tradeoff are investigated and discussed along with future perspective and possible fundamental limitations
Graphene on Silicon Modulators
No full textGraphene is a 2D material with appealing electronic and optoelectronic properties. It is a zero-bandgap material with valence and conduction bands meeting in a single point (Dirac point) in the momentum space. Its conductivity can be changed by shifting the Fermi level energy via an external electric field. This important property determines broadband and tunable absorption at optical frequencies. Moreover, its conductivity is a complex quantity, i.e., Graphene exhibits both electro-absorption and electro-refraction tunability, and this is an intriguing property for photonic applications. For example, it can be combined as an active material for silicon waveguides to realize efficient detectors, switches, and modulators. In this article, we review our results in the field, focusing on graphene- based optical modulators integrated on Silicon photonic platforms. Results obtained in the fabrication of single and double-layer capacitive modulators are reported showing intensity and phase modulation, resilience of the generated signals to chromatic dispersion because of proper signal chirp and operation up to 50 Gb/s
Temperature-Dependence of Ge on Si p-i-n Photodetectors
No full textWe investigate the temperature dependence of germanium on silicon p-i-n photodetectors in terms of both dark current density and near-infrared responsivity. The dark current increases by nearly a factor 1.6 every 10 degrees C, consistently with carrier generation in the space charge region. The responsivity has a complex trend, its temperature variation depending on wavelength and on the germanium quality. Detectors with a large defect density in the active layer exhibit a reduced responsivity as the temperature increases
Near-Infrared Ge-on-Si Power Monitors Monolithically Integrated on SOI Chips
No full textWe realize and test power monitors monolithically integrated on silicon-on-insulator optical chips. The devices consist of near-infrared waveguide photodetectors in evaporated germanium with front-end transimpedance amplifiers. The power monitors operate with signals as small as 10nW, with errors below 0.2% and 2% at 1 and 0.1 mu W, respectively
Near-Infrared Photodetectors in Evaporated Ge: Characterization and TCAD Simulations
No full text"Thermal evaporation of germanium (Ge) on silicon (Si) has proved to be a suitable technique for the fabrication of high responsivity, low-cost, near-infrared pn detectors. Such results rely on low-temperature diffusion of n-type dopants. The corresponding transport phenomena are quite involved and cannot be described by standard models for pn junctions because of rather large defect concentration density in the Ge layer. In this paper, we report on fabrication, characterization, and simulation of defected Ge on Si photodiodes. For the simulations, we developed a technology computer aided design model and hereby demonstrate its ability to reproduce the measured optoelectronic characteristics of the devices.
TCAD simulation of thermally evaporated germanium
No full textEpitaxial growth of germanium on silicon produces large misfit and threading dislocation densities which dramatically affect electronic properties of Ge. For this reason, TCAD standard models and parameters, optimized for bulk Ge, fail when applied to Ge epilayers. In this work we describe a novel approach for the simulation of highly defected germanium films grown by thermal evaporation. We also take into account the gradient of defect concentration depending on the germanium thickness. The proposed model is successfully employed for TCAD simulations of Ge-on-Si pn heterojunction photodiodes, demonstrating good agreement with experimental data. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
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