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  2. Dr Konstantin Stefanov

Dr Konstantin Stefanov

Profile summary

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.  


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 groups

NameTypeParent Unit
e2v Centre for Electronic ImagingCentreFaculty of Science


Externally funded projects

[Te2v] CIS123 7µm
RoleStart dateEnd dateFunding source
Lead01 Nov 202031 Oct 2021e2v Teledyne e2v

Simulation of a variant of the CIS123 TDI CMOS image sensor with 7 µm pixel pitch.

ESA NPI Gaia radiation damage
RoleStart dateEnd dateFunding source
Co-investigator01 Sep 202031 Aug 2023ESA (European Space Agency)

European Space Agency (ESA) Network Partnering Initiative (NPI) funding to support PhD student Saad Ahmed, who is working on radiation damage of the Gaia focal plane detectors. This funding will allow Saad to work more closely with ESA using in-orbit calibration data from the Gaia space telescope, and to get access to test equipment located at the ESA Research and Technology Centre (ESTEC) in Holland.

[Te2v] CIS123 Rev.E
RoleStart dateEnd dateFunding source
Lead01 Jun 202031 May 2021e2v Teledyne e2v

Simulations and characterisation of the TDI CMOS chip CIS123 Rev.E provided by Te2v.

Theseus CMOS Sensor Development – ESA TDE Activity
RoleStart dateEnd dateFunding source
Co-investigator01 Nov 201931 Oct 2021ESA (European Space Agency)

The project aims to develop a new type of X-ray sensor based on CMOS image sensor technology, initially for ESA’s M5 mission candidate Theseus, but with butch broader ranging impact across science and synchrotron science.

[Te2v] CIS123 Rev. D Characterisation
RoleStart dateEnd dateFunding source
Lead02 Sep 201931 Dec 2019e2v Teledyne e2v

Characterisation of CIS123 Revision D, a TDI CMOS image sensor developed by Teledyne e2v.

TDI CMOS Device Simulations
RoleStart dateEnd dateFunding source
Lead01 May 201931 May 2019e2v Teledyne e2v

Simulations in TCAD of TDI CMOS structures for implementation in manufacturing process by Te2v.

[ATTRACT] Single Photon Visible Light Image Sensors for Science and Technology
RoleStart dateEnd dateFunding source
Lead01 Mar 201929 Feb 2020EC (European Commission): FP (inc. Horizon Europe, H2020, ERC);CERN European Council for Nuclear Research (Conseil Européen pour la Recherche Nucléaire)

This project will investigate innovative ways to realise single photon visible light imagers for a number of high growth areas in science and technology. The main objective is to create image sensor designs suitable for adaptive optics systems and low-light level spectroscopic and imaging applications, based on detailed semiconductor and technology device simulations. By detecting and counting each and every photon without any additional noise, these sensors could offer the ultimate performance in imaging, and help us see and discover the unknown. The work will focus on designing of Complementary Metal Oxide Semiconductor (CMOS) image sensors with deep sub-electron readout noise and high frame rate. Reliable single photon imaging from large sensors would offer a breakthrough in performance, and the results of this project are expected to lay the foundations for transformational changes to low-light imaging in science and technology.

[Te2v] HiRho image sensor development
RoleStart dateEnd dateFunding source
Lead01 Dec 201801 Mar 2019e2v Teledyne e2v

In this project the CEI will carry out Technology CAD (TCAD) modelling to support the design of a 2k x 2k high performance image sensor with increased sensitivity at near-infrared wavelengths. The principle of operation of the sensor was invented at the OU and involves specialised pixel structure that allows the substrate to be reverse biased and fully depleted. The CEI will simulate the geometry, the doping profile and the electrical performance of the pixel to be included in the new imager. The work is done in support of Teledyne e2v (Te2v) from their contract with the European Space Agency.

[Te2v] : Ruby Heavy Ion Tests
RoleStart dateEnd dateFunding source
Lead01 Dec 201830 Nov 2019e2v Teledyne e2v

Teledyne e2v have developed new versions of the EV76C660 and EV76C661 (the Ruby family) CMOS image sensors with increased resistance to single event effects from radiation in space applications. Previous heavy ion tests on the EV76C660 sensor conducted by the CEI have revealed much improved resistance to single event latch-ups. In this project Teledyne e2v are requesting the CEI to perform additional heavy ion testing on the new EV76C661 CMOS image sensor in order to investigate the suitability of the device for space applications.

STFC Open 2018 DTP
RoleStart dateEnd dateFunding source
Co-investigator01 Oct 201830 Sep 2022STFC Science & Technology Facilities Council

STFC Open 2018 DTP

[Te2v] ONYX Heavy Ion Testing
RoleStart dateEnd dateFunding source
Lead01 Oct 201831 Mar 2019e2v Teledyne e2v

Teledyne e2v have developed the EV76C664 (Onyx) CIS which is part of the same family of CIS as the EV76C660 (Ruby) and EV76C560 (Sapphire) CIS. The CEI has performed extensive TID, TNID and HIT campaigns on both the Ruby and Sapphire CIS and has flown the Sapphire CIS in the C3D instrument on UKube-1 and the C3D2 instrument on AlSat Nano. Teledyne e2v are requesting CEI perform Heavy Ion Testing on the Teledyne e2v EV76C664 (Onyx) CMOS Image Sensor to investigate the suitability of the device for space applications.

TDI CMOS Prototype Camera
RoleStart dateEnd dateFunding source
Lead01 Apr 201809 Nov 2021CEOI Centre for Earth Observation Instrumentation

Teledyne-e2v have a new CMOS technology suitable for Time Delay Integration (TDI) operation, commonly used in optical payloads for Earth Observation. In this project, Teledyne-e2v will manufacture these new TDI CMOS devices and they will be integrated and tested by Surrey Satellite Technology (SSTL) Optical Payloads Group and the CEI. The result will be a high-TRL TDI CMOS-based engineering model (EM) camera system integrated with SSTL's newest optical telescope, that could be further developed to a flight model for a future technology demonstration mission (out of scope for this call).

NSTP3-R1/e2v Characterisation of TDI CMOS
RoleStart dateEnd dateFunding source
Lead01 Jan 201714 Jun 2019UKSA 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 2021UKSA 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.