Imperial College London

DrKristelFobelets

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Reader in Microelectronics Engineering
 
 
 
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Contact

 

+44 (0)20 7594 6236k.fobelets Website

 
 
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Assistant

 

Mrs Jay Sahote +44 (0)20 7594 6215

 
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Location

 

714Electrical EngineeringSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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152 results found

Delgado-Notario JA, Javadi E, Calvo-Gallego J, Diez E, Meziani YM, Velazquez-Perez JE, Fobelets Ket al., 2018, Sub-THz Response of Strained-Silicon MODFETs, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, Vol: 215, ISSN: 1862-6300

JOURNAL ARTICLE

Delgado-Notario JA, Velazquez-Perez JE, Meziani YM, Fobelets Ket al., 2018, Sub-THz Imaging Using Non-Resonant HEMT Detectors., Sensors (Basel), Vol: 18

Plasma waves in gated 2-D systems can be used to efficiently detect THz electromagnetic radiation. Solid-state plasma wave-based sensors can be used as detectors in THz imaging systems. An experimental study of the sub-THz response of II-gate strained-Si Schottky-gated MODFETs (Modulation-doped Field-Effect Transistor) was performed. The response of the strained-Si MODFET has been characterized at two frequencies: 150 and 300 GHz: The DC drain-to-source voltage transducing the THz radiation (photovoltaic mode) of 250-nm gate length transistors exhibited a non-resonant response that agrees with theoretical models and physics-based simulations of the electrical response of the transistor. When imposing a weak source-to-drain current of 5 μA, a substantial increase of the photoresponse was found. This increase is translated into an enhancement of the responsivity by one order of magnitude as compared to the photovoltaic mode, while the NEP (Noise Equivalent Power) is reduced in the subthreshold region. Strained-Si MODFETs demonstrated an excellent performance as detectors in THz imaging.

JOURNAL ARTICLE

Panteli C, Georgiou P, Fobelets K, 2018, Performance improvement of commercial ISFET sensors using reactive ion etching, Microelectronic Engineering, Vol: 192, Pages: 61-65, ISSN: 0167-9317

© 2018 Elsevier B.V. Reactive Ion Etching (RIE) is used to improve the performance of commercial Complementary Metal Oxide Semiconductor (CMOS) Ion-Sensitive Field-Effect Transistors (ISFETs) by thinning the top passivation layers inherent of the CMOS fabrication process. Using a combination of O2 and SF6 in 50% ratio, both polyimide and Si3N4 layers are etched in one etching step. Etching for different times we find the right remaining layer thickness for best ISFET performance to be ∼1 μm of SiO2. The results show an increase in pH sensitivity of 125%, a 5700% increase in passivation capacitance and a 96% reduction in capacitive attenuation. The RIE etch recipe can be used on multi-project wafers (MPW) to boost CMOS sensor performance.

JOURNAL ARTICLE

Shougee A, Konstantinou F, Albrecht T, Fobelets Ket al., 2018, Cyclic Voltammetry Peaks Due to Deep Level Traps in Si Nanowire Array Electrodes, IEEE TRANSACTIONS ON NANOTECHNOLOGY, Vol: 17, Pages: 154-160, ISSN: 1536-125X

JOURNAL ARTICLE

Delgado Notario JA, Javadi E, Calvo-Gallego J, Diez E, Velazquez JE, Meziani YM, Fobelets Ket al., 2017, Sub-Micron Gate Length Field Effect Transistors as Broad Band Detectors of Terahertz Radiation, 5th Russia-Japan-USA-Europe Symposium on Fundamental and Applied Problems of Terahertz Devices and Technologies (RJUSE-TeraTech), Publisher: WORLD SCIENTIFIC PUBL CO PTE LTD, Pages: 87-95, ISSN: 1793-1274

CONFERENCE PAPER

Delgado Notario JA, Javadi E, Clerico V, Fobelets K, Otsuji T, Diez E, Velazquez-Perez JE, Meziani YMet al., 2017, Experimental and theoretical studies of Sub-THz detection using strained-Si FETs, 20th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

CONFERENCE PAPER

Delgado Notario JA, Javadi E, Velazquez JE, Diez E, Meziani YM, Fobelets Ket al., 2017, Detection of terahertz radiation using submicron field effect transistors and their use for inspection applications, Conference on Millimetre Wave and Terahertz Sensors and Technology X, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

CONFERENCE PAPER

Konstantinou F, Shougee A, Albrecht T, Fobelets Ket al., 2017, TiO2 coated Si nanowire electrodes for electrochemical double layer capacitors in room temperature ionic liquid, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 50, ISSN: 0022-3727

JOURNAL ARTICLE

Qiao L, Shougee A, Albrecht T, Fobelets Ket al., 2016, Oxide-coated silicon nanowire array capacitor electrodes in room temperature ionic liquid, ELECTROCHIMICA ACTA, Vol: 210, Pages: 32-37, ISSN: 0013-4686

JOURNAL ARTICLE

Delgado-Notario JA, Meziani YM, Velazquez-Perez JE, Fobelets Ket al., 2015, Optimization of THz response of strained-Si MODFETs, E-MRS Spring Meeting / Symposium H / Symposium I / Symposium BB / Symposium FF / Symosium D, Publisher: WILEY-V C H VERLAG GMBH, Pages: 1401-1404, ISSN: 1862-6351

CONFERENCE PAPER

Meziani YM, Morozov S, Notario JAD, Maremyanin K, Velazquez JE, Fobelets Ket al., 2015, Enhancement of sub-terahertz detection by drain-to-source biasing on strained silicon MODFET devices, 19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON '19), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

CONFERENCE PAPER

Rahman T, Fobelets K, 2015, Efficient tool flow for 3D photovoltaic modelling, COMPUTER PHYSICS COMMUNICATIONS, Vol: 193, Pages: 124-130, ISSN: 0010-4655

JOURNAL ARTICLE

Fobelets K, Meghani M, Li C, 2014, Influence of Minority Carrier Gas Donors on Low-Frequency Noise in Silicon Nanowires, IEEE TRANSACTIONS ON NANOTECHNOLOGY, Vol: 13, Pages: 1176-1180, ISSN: 1536-125X

JOURNAL ARTICLE

Fobelets K, Utke I, 2014, Nano Fabrication 2013 Preface, MICROELECTRONIC ENGINEERING, Vol: 121, Pages: VII-VII, ISSN: 0167-9317

JOURNAL ARTICLE

Rahman T, Navarro-Cia M, Fobelets K, 2014, High density micro-pyramids with silicon nanowire array for photovoltaic applications, NANOTECHNOLOGY, Vol: 25, ISSN: 0957-4484

JOURNAL ARTICLE

Xu B, Fobelets K, 2014, Spin-on-doping for output power improvement of silicon nanowire array based thermoelectric power generators, JOURNAL OF APPLIED PHYSICS, Vol: 115, ISSN: 0021-8979

JOURNAL ARTICLE

Xu B, Khouri W, Fobelets K, 2014, Two-Sided Silicon Nanowire Array/Bulk Thermoelectric Power Generator, IEEE ELECTRON DEVICE LETTERS, Vol: 35, Pages: 596-598, ISSN: 0741-3106

JOURNAL ARTICLE

Fobelets K, Ahmad MM, Roumyantsev S, Shur Met al., 2013, Influence of ambient on conductivity and 1/f noise in Si nanowire arrays, 22nd International Conference on Noise and Fluctuations (ICNF), Publisher: IEEE

CONFERENCE PAPER

Fobelets K, Li C, Coquillat D, Arcade P, Teppe Fet al., 2013, THz response of silicon nanowire arrays, Journal of Materials Chemistry

JOURNAL ARTICLE

Fobelets K, Li CB, Coquillat D, Arcade P, Teppe Fet al., 2013, Far infrared response of silicon nanowire arrays, RSC ADVANCES, Vol: 3, Pages: 4434-4439, ISSN: 2046-2069

JOURNAL ARTICLE

Li C, Fobelets K, Liu C, Xue C, Cheng B, Wang Qet al., 2013, Ag-assisted lateral etching of Si nanowires and its application to nanowire transfer, APPLIED PHYSICS LETTERS, Vol: 103, ISSN: 0003-6951

JOURNAL ARTICLE

Li C, Zhang C, Fobelets K, Zheng J, Xue C, Zuo Y, Cheng B, Wang Qet al., 2013, Impact of ammonia on the electrical properties of p-type Si nanowire arrays, JOURNAL OF APPLIED PHYSICS, Vol: 114, ISSN: 0021-8979

JOURNAL ARTICLE

Meziani YM, Garcia-Garcia E, Velazquez-Perez JE, Coquillat D, Dyakonova N, Knap W, Grigelionis I, Fobelets Ket al., 2013, Terahertz imaging using strained-Si MODFETs as sensors, SOLID-STATE ELECTRONICS, Vol: 83, Pages: 113-117, ISSN: 0038-1101

JOURNAL ARTICLE

Meziani YM, Garcia-Garcia E, Velazquez-Perez JE, Coquillat D, Dyakonova N, Knap W, Grigelionis I, Fobelets Ket al., 2013, Terahertz imaging using strained-Si MODFETs as sensors, Solid State Electronics, Vol: 83, Pages: 113-117

We report on non-resonant (broadband) and resonant detection of terahertz radiation using strained-Si modulation doped field effect transistors. The devices were excited at room temperature by two types of terahertz sources (an electronic source based on frequency multipliers at 0.292 THz and a pulsed parametric laser at 1.5 THz). In both cases, a non-resonant response with maxima around the threshold voltage was observed. Shubnikov-de Haas and photoresponse measurements were performed simultaneously and showed a phase-shift of π/2 in good agreement with the theory, which demonstrates that the observed response is related to the plasma waves oscillation in the channel. The non-resonant features were used to demonstrate the capabilities of such devices in terahertz imaging. We also cooled our device down to 4.2 K to increase the quality factor and resonant detection was observed by using a tunable source of terahertz radiation.

JOURNAL ARTICLE

Meziani YM, Velazquez-Perez JE, Garcia-Garcia E, Coquillat D, Dyakonova N, Knap W, Grigelionis I, Fobelets Ket al., 2013, Terahertz detection using Si-SiGe MODFETs, 9th Spanish Conference on Electron Devices (CDE), Publisher: IEEE, Pages: 167-170, ISSN: 2163-4971

CONFERENCE PAPER

Rahman T, Fobelets K, 2013, Simulation of Rough Silicon Nanowire Array for use in Spin-On-Doped PN core-shell Solar Cells, UKSim-AMSS 7th European Modelling Symposium on Computer Modelling and Simulation (EMS), Publisher: IEEE, Pages: 725-729, ISSN: 2473-3539

CONFERENCE PAPER

Rahman T, Fobelets K, Meziani YM, Velazquez-Perez JEet al., 2013, Highly Doped Nanowire Array for Use in Hybrid Silicon/Polymer Junction Solar Cells, 223rd ECS Meeting

CONFERENCE PAPER

Xu B, Fobelets K, 2013, Efficiency Improvement of Silicon Nanowire Arrays (NWAs) Thermoelectric Power Generation (TEG) by Spin On Doping (SOD), 223rd ECS Meeting

CONFERENCE PAPER

Xu B, Li C, Myronov M, Fobelets Ket al., 2013, n-Si-p-Si1-xGex nanowire arrays for thermoelectric power generation, SOLID-STATE ELECTRONICS, Vol: 83, Pages: 107-112, ISSN: 0038-1101

JOURNAL ARTICLE

Xu B, Li CB, Myronov M, Fobelets Ket al., 2013, n-Si–p-Si1−xGex nanowire arrays for thermoelectric power generation, Solid State Electronics, Vol: 83, Pages: 107-112

The output power of a discrete assembly of n-Si–p-Si1−xGex (0 ⩽ x ⩽ 0.4) thermoelectric generators is measured as a function of load resistance. The influence of Ge content and nanowire structures on the performance of thermoelectric devices is evaluated in measurements around room temperature. The nanowire arrays are etched using a metal induced local oxidation and etching process, based on self-assembled Ag nanoparticles and HF. The use of nanowires and SiGe with dimensions smaller than 30 μm, is beneficial for an improvement of, at least, a factor of 10 in the output power. However, better performance improvements can be obtained by optimising the thermal and electrical contact resistances at the interfaces. Optimisation of the electrical contact results in a performance boost by a factor of 25.

JOURNAL ARTICLE

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