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Dr Konstantin Stefanov

Profile summary

  • Research Staff
  • Senior Research Fellow
  • Faculty of Science, Technology, Engineering & Mathematics
  • School of Physical Sciences
  • konstantin.stefanov

Professional biography

Presently I am Senior Research Fellow at the Centre for Electronic Imaging (CEI). Most of my work is focused on the design and evaluation of novel image sensors for scientific applications, manufactured in CMOS technology. The research topics I am working on now are electron multiplication in CMOS imagers, achieving full depletion in CMOS sensors for maximum quantum efficiency, dynamic charge collection effects in CCDs, and radiation damage effects.

From 2001-2008 I worked at STFC Rutherford Appleton Laboratory (RAL) on the development of 3 generations of column-parallel CCDs and 2 generations of CMOS-based in-situ storage image sensors, readout ASICs and support electronics for the vertex detector at the proposed International Linear Collider. I also lead the development of one of the first devices in the world incorporating buried channel CCD in specially modified 0.18 μm CMOS process.

From 2008-2012 I was with the technology consultancy company Sentec Ltd. in Cambridge (UK), working on a variety of new technologies for industrial and consumer applications.  

Qualifications

MSc in Applied Physics from Sofia University, Bulgaria (1994).

PhD in Physics from Saga University, Japan (2001).

Research interests

My research interests are in semiconductor image sensors for science, where the term "imaging" covers everything from infrared, visible and X-ray wavelengths to minimum ionising particles in high energy physics.

  • High performance CCDs
  • CMOS image sensors
  • Monolithic "CCD in CMOS" devices
  • Semiconductor physics
  • Device simulations
  • Radiation damage effects in semiconductors and their influence on device performance
  • Detector electronics and data acquisition systems

Research Activity

Research groups

NameTypeParent Unit
e2v Centre for Electronic ImagingCentreFaculty of Science

 

Externally funded projects

NSTP3-R1/e2v Characterisation of TDI CMOS

RoleStart dateEnd dateFunding source
Lead01/Jan/201731/Dec/2017UKSA UK Space Agency
The CEI have been invited by e2v to collaborate on a bid into the UKSA NSTP3-R1 call, with e2v as the lead organisation. The CEI element of this bid is to perform electro-optic characterisation of a new Time Delay Integration (TDI) CMOS image sensor developed by e2v before and after gamma irradiation of the sensor.

ESA p-channel contract change notification

RoleStart dateEnd dateFunding source
Co-investigator05/Sep/201601/Sep/2017ESA (European Space Agency)
The CEI have been working under contract to ESA (CLS-404-14) on an investigation in the performance characterisation and radiation testing of p-channel CCDs. This work is now nearing completion and ESA have indicated that they would like to fund an additional study under a contract change notification (CCN). This additional study will focus on the evolution of defects within a back illuminated p-channel and n-channel CCD204 after the devices have been irradiated, side-by-side, and for a period of time after, whilst cold annealing takes place.

CMOS Image Sensors for Precision Astronomy

RoleStart dateEnd dateFunding source
Lead01/Apr/201631/Mar/2020STFC (Science & Technology Facilities Council)
The subject of this project will be high performance CMOS imagers with high quantum efficiency, low noise and high frame rate for demanding science applications such as ground and space-based astronomy. This studentship will contribute to the detailed characterisation and understanding of the complex nature of those sensors, and will help develop imagers with improved characteristics.

JUICE phases B2/C/D

RoleStart dateEnd dateFunding source
Co-investigator01/Apr/201531/Mar/2020UKSA UK Space Agency
This phase of the grant is to cover the "build phase" (B2/C/D) of ESA's JUICE mission. The CEI will procure, qualify and test the flight model detectors and supply them to DLR for integration into the flight camera. During this project the CEI will provide design inputs to the JANUS camera consortium, support formal ESA meetings, reviews, and telecons with documentation, study the trade-offs in the use of the sensors, particularly recommending operating temperature and temperature stability, and the strategy for removing prompt electron events from the images. We are also completing the modelling of the effects of electron radiation on mission science and image quality, and will perform qualification radiation damage assessment on the technology with protons, electrons, gammas and heavy ions. The CEI will also perform acceptance radiation damage assessment on devices from the flight wafer.

CMOS Image Sensors with High Quantum Efficiency

RoleStart dateEnd dateFunding source
Lead18/Feb/201530/Sep/2016UKSA UK Space Agency
One of the main image sensors for space applications today is the CCD due to its high image quality, low noise and large sensitive area. Through back illumination of fully depleted devices the CCD demonstrates quantum efficiency (QE) above 90% over much of the visible range. Over recent years, new CMOS image technology has been under development and now can achieve similar low noise and large area, however, deep depletion has remained elusive due to the more complex CMOS structure, combined with typically low operating voltages. This project aims to develop the next generation of CMOS image sensors suitable for Earth observation, ground and space-based astronomy, and other science applications requiring high QE in the red and near-infrared parts of the spectrum. The main innovation is the achievement of high QE by full depletion of the thick sensitive semiconductor layer using reverse substrate bias. In this way sensitive detector thickness of 100 µm or more can be realised, instead of the current 5-10 µm thick devices. The development will concentrate on building silicon CMOS image sensors using pinned photodiode photosensitive elements, capable of achieving science-grade imaging performance. The technological advances from this work will allow many space-based imaging instruments to transition from CCD to CMOS devices and benefit from better radiation hardness, higher readout speeds, increased level of integration and lower power dissipation. At the Centre for Electronic Imaging (CEI), based at the Open University, we have performed preliminary modelling and have filed a patent application to enable the construction of fully depleted CMOS image sensors using reverse substrate bias. Under this programme we would aim to design, manufacture and test prototype CMOS image sensors based on our patent application.

Publications

Fully Depleted Pinned Photodiode CMOS Image Sensor With Reverse Substrate Bias (2017-01-03)
Stefanov, Konstantin D.; Clarke, Andrew S. and Holland, Andrew D.
IEEE Electron Device Letters, 38(1) (pp. 64-66)
Comparison of Point Spread Function in p- and n-Channel CCDs (2015-08-07)
Murray, N. J.; Allanwood, E. A. H.; Dryer, B. J.; Weatherill, D. P.; Stefanov, K. D.; Holland, A. D. and Burt, D. J.
Journal of Instrumentation, 10, Article C08007(8)
Fully depleted, thick, monolithic CMOS pixels with high quantum efficiency (2015-04-30)
Clarke, A.; Stefanov, K.; Johnston, N. and Holland, A.
Journal of Instrumentation, 10, Article T04005(4)
Digital CDS for image sensors with dominant white and 1/f noise (2015-04-08)
Stefanov, Konstantin
Journal of Instrumentation, 10, Article P04003(4)
Characterisation of a CMOS charge transfer device for TDI imaging (2015-03-18)
Rushton, J.; Holland, A.; Stefanov, K. and Mayer, F.
Journal of Instrumentation, 10, Article C03027(3)
Non-linear responsivity characterisation of a CMOS Active Pixel Sensor for high resolution imaging of the Jovian system (2015-02-09)
Soman, M.; Stefanov, K.; Weatherill, D.; Holland, A.; Gow, J. and Leese, M.
Journal of Instrumentation, 10, Article C02012(2)
Analytical investigation of correlated charge collection in CCDs (2015-02-02)
Weatherill, D. P.; Stefanov, K. D.; Holland, A. D. and Jordan, D.
Journal of Instrumentation, 10, Article C02002(2)
Optimal digital correlated double sampling for CCD signals (2014-07-03)
Stefanov, K. D. and Murray, N. J.
Electronics Letters, 50(14) (pp. 1022-1024)
A statistical model for signal-dependent charge sharing in image sensors (2014-01)
Stefanov, Konstantin D.
IEEE Transactions on Electron Devices, 61(1) (pp. 110-115)
Simulations of charge transfer in Electron Multiplying Charge Coupled Devices (2014)
Bush, N.; Stefanov, K.; Hall, D.; Jordan, D. and Holland, A.
Journal of Instrumentation, 9, Article C12042(12)
Performance of deep-depletion buried-channel n-MOSFETs for CMOS image sensors (2013-12)
Stefanov, Konstantin D.; Zhang, Zhige; Damerell, Chris; Burt, David and Kar-Roy, Arjun
IEEE Transactions on Electron Devices, 60(12) (pp. 4173-4179)
Design and performance of a CMOS study sensor for a binary readout electromagnetic calorimeter (2011-05)
Ballin, J. A.; Coath, R.; Crooks, J. P.; Dauncey, P. D.; Magnan, A. -M.; Mikami, Y.; Miller, O. D.; Noy, M.; Rajovic, V.; Stanitzki, M.; Stefanov, K. D.; Turchetta, R.; Tyndel, M.; Villani, E. G.; Watson, N. K.; Wilson, J. A. and Zhang, Z.
Journal of Instrumentation, 6, Article P05009(5)
First results with prototype ISIS devices for ILC vertex detector (2010-12-11)
Damerell, C.; Zhang, Z.; John, J. J.; Li, Y.; Nomerotski, A.; Holland, A.; Seabroke, G.; Havranek, M.; Stefanov, K.; Kar-roy, A.; Bell, R.; Burt, D. and Pool, P.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 624(2) (pp. 465-469)
Design and performance of improved Column Parallel CCD, CPC2 (2010-09-01)
Banda, Y.; Coulter, P.; Cussans, D.; Damerell, C.; Devetak, E.; Fopma, J.; Foster, B.; Frost, R.; Gao, R.; Goldstein, J.; Greenshaw, T.; Harder, K.; Hawes, B.; Hillert, S.; Jeffery, B.; John, J. J.; Kundu, N.; Li, Y.; Murray, P.; Nomerotski, A.; Perry, C.; Stefanov, K.; Thomas, S.; Velthuis, J.; Woolliscroft, T.; Worm, S.; Yow, J. and Zhang, Z.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 621(1-3) (pp. 192-204)
Readout chip for Column Parallel CCD, CPR2A (2009-08-21)
Havranek, M.; Murray, P.; Stefanov, K.; Thomas, S.; Damerell, C.; Fopma, J.; Goldstein, J.; Greenshaw, T.; Hawes, B.; Nomerotski, A.; Woolliscroft, T.; Worm, S. and Zhang, Z.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 607(3) (pp. 640-647)
Charge shielding in the In-situ Storage Image Sensor for a vertex detector at the ILC (2009-08-21)
Zhang, Z.; Stefanov, K. D.; Bailey, D.; Banda, Y.; Buttar, C.; Cheplakov, A.; Cussans, D.; Damerell, C.; Devetak, E.; Fopma, J.; Foster, B.; Gao, R.; Gillman, A.; Goldstein, J.; Greenshaw, T.; Grimes, M.; Halsall, R.; Harder, K.; Hawes, B.; Hayrapetyan, K.; Heath, H.; Hillert, S.; Jackson, D.; Pinto Jayawardena, T.; Jeffery, B.; John, J.; Johnson, E.; Kundu, N.; Laing, A.; Lastovicka, T.; Lau, W.; Lintern, A.; Lynch, C.; Mandry, S.; Martin, V.; Murray, P.; Nichols, A.; Nomerotski, A.; Page, R.; Parkes, C.; Perry, C.; O'Shea, V.; Sopczak, A.; Tabassam, H.; Tikkanen, T.; Velthuis, J.; Walsh , R.; Woolliscroft, T. and Worm, S.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 607(3) (pp. 538-543)
Modeling of charge transfer inefficiency in a CCD with high-speed column parallel readout (2009-06)
Sopczak, André; Aoulmit, Salim; Bekhouche, Khaled; Bowdery, Chris; Buttar, Craig; Damerell, Chris; Djendaoui, Dahmane; Dehimi, Lakhdar; Greenshaw, Tim; Koziel, Michal; Maneuski, Dzmitry; Nomerotski, Andrei; Stefanov, Konstantin; Tikkanen, Tuomo; Woolliscroft, Tim and Worm, Steve
IEEE Transactions on Nuclear Science, 56(3) (pp. 1613-1617)
e2v CMOS and CCD sensors and systems for astronomy (2017-07-05)
Jorden, P. R.; Jerram, P. A.; Fryer, M. and Stefanov, K. D.
In : Precision Astronomy with Fully Depleted CCDs (PACCD2016) (1-2 Dec 2016, Brookhaven National Laboratory, USA)
Single event effects in 0.18 μm CMOS image sensors (2016-08-05)
Rushton, Joseph E.; Stefanov, Konstantin D.; Holland, Andrew D.; Bugnet, Henri; Mayer, Frederic; Cordrey-Gale, Matthew and Endicott, James
In : High Energy, Optical, and Infrared Detectors for Astronomy VII (26 June - 1 July 2016, Edinburgh, United Kingdom)
Validation of NIEL for >1MeV electrons in silicon using the CCD47-20 (2016-08-05)
Dryer, B.; Smith, P.; Nuns, T.; Murray, N.; Stefanov, K. D.; Gow, J. P. D.; Burgon, R.; Hall, D. J. and Holland, A. D.
In : High Energy, Optical, and Infrared Detectors for Astronomy VII (26 June - 1 July 2016, Edinburgh, United Kingdom)
Electro-optic and radiation damage performance of the CIS115, an imaging sensor for the JANUS optical camera on-board JUICE (2016-08-01)
Soman, M. R.; Allanwood, E. A. H.; Holland, A. D.; Stefanov, K.; Pratlong, J.; Leese, M.; Gow, J. P. D. and Smith, D. R.
In : High Energy, Optical, and Infrared Detectors for Astronomy VII (June 26 2016, Edinburgh)
Low Voltage Electron Multiplying CCD in a CMOS Process (2016-07-27)
Dunford, Alice; Stefanov, Konstantin and Holland, Andrew
In : SPIE Astronomical Telescopes + Instrumentation (AS16) (26 June - 1 July 2016, Edinburgh, UK)
Fully depleted and backside biased monolithic CMOS image sensor (2016-07-27)
Stefanov, Konstantin D.; Clarke, Andrew S. and Holland, Andrew D.
In : High Energy, Optical, and Infrared Detectors for Astronomy VII (25-30 June 2016) (p 991513)
A global shutter CMOS image sensor for hyperspectral imaging (2015-09-22)
Stefanov, Konstantin D.; Dryer, Ben. J.; Hall, David J.; Holland, Andrew D.; Pratlong, Jérôme; Fryer, Martin and Pike, Andrew
In : UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VII (9 August 2015, San Diego, CA)
Proton-induced Random Telegraph Signal in the CMOS imaging sensor for JANUS, the visible imaging telescope on JUICE (2015-09-22)
Winstone, G. P.; Soman, M. R.; Allanwood, E. A. H.; Holland, A. D.; Gow, J. P. D.; Stefanov, K. and Leese, M.
In : UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VII (9 August 2015, San Diego, CA) (96020N)
A CMOS TDI image sensor for Earth observation (2015-09-01)
Rushton, Joseph E.; Stefanov, Konstantin D.; Holland, Andrew D.; Endicott, James; Mayer, Frederic and Barbier, Frederic
In : Nanophotonics and Macrophotonics for Space Environments IX (13-15 August 2015, San Diego, CA)
Proton irradiation of the CIS115 for the JUICE mission (2015-09)
Soman, M. R.; Allanwood, E. A. H.; Holland, A. D.; Winstone, G. P.; Gow, J. P. D.; Stefanov, K. and Leese, M.
In : UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VII (9 August 2015, San Diego, CA)
Models for dynamic correlated charge collection effects in thick CCDs (2015-08)
Weatherill, Daniel P.; Stefanov, Konstantin; Jordan, Douglas; Holland, Andrew and Kotov, Ivan V.
In : UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VII (09-13 August 2015, San Diego, CA)
Modelling and testing the x-ray performance of CCD and CMOS APS detectors using numerical finite element simulations (2014-07-23)
Weatherill, Daniel P.; Stefanov, Konstantin D.; Greig, Thomas A. and Holland, Andrew D.
In : SPIE Astronomical Telescopes and Instrumentation (22 - 25 June 2014, Montreal)
Assessment of the performance and radiation damage effects under cryogenic temperatures of a P-channel CCD204s (2014)
Murray, Neil J.; Holland, Andrew D.; Gow, Jason P. D.; Hall, David J.; Stefanov, Konstantin D.; Dryer, Ben J.; Barber, Simeon and Burt, David J.
In : High Energy, Optical, and Infrared Detectors for Astronomy VI (22-27 July 2014, Montréal, Quebec)
Design and characterisation of the new CIS115 sensor for JANUS, the high resolution camera on JUICE (2014)
Soman, Matthew; Holland, Andrew; Stefanov, Konstantin; Gow, Jason; Leese, Mark; Pratlong, Jérôme and Turner, Peter
In : High Energy, Optical, and Infrared Detectors for Astronomy VI (22 - 25 June 2014, Montreal)
Performance of buried channel n-type MOSFETs in 0.18-μm CMOS image sensor process (2013-09-26)
Stefanov, Konstantin D.; Zhang, Zhige; Damerell, Chris; Burt, David and Kar-Roy, Arjun
In : UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XVIII (25 August 2013, San Diego)
Multi-level parallel clocking of CCDs for: improving charge transfer efficiency, clearing persistence, clocked anti-blooming, and generating low-noise backgrounds for pumping (2013-09-26)
Murray, Neil J.; Burt, David J.; Holland, Andrew D.; Stefanov, Konstantin D.; Gow, Jason P. D.; MacCormick, Calum; Dryer, Ben J. and Allanwood, Edgar A. H.
In : UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VI (25-26 August 2013, San Diego)
Point-spread function and photon transfer of a CCD for space-based astronomy (2013)
Allanwood, Edgar A. H.; Murray, Neil J.; Stefanov, Konstantin D.; Burt, David J. and Holland, Andrew D.
In : UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VI, (25-26 August 2013, San Diego)
Total ionizing dose effects on I-V and noise characteristics of MOS transistors in a 0.18 μm CMOS Image Sensor process (2013)
Greig, Thomas; Stefanov, Konstantin; Holland, Andrew; Clarke, Andrew; Burt, David and Gow, Jason
In : 14th European Conference on Radiation and Its Effects on Components and Systems (RADECS) (23-27 Sept. 2013, Oxford)
CMOS image sensor (2015-09-16)
Stefanov, Konstantin

Smart power source (2013-07-04)
Bourilkov, Jordan; Specht, Steven; Coronado, Sergio; Stefanov, Konstantin and Ayoz, Suat

Sensor Signal Sampling (2013-05-16)
Colby, Edward; Storkey, Matthew; Healy, David and Stefanov, Konstantin

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