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Characterization of interface states & radiation damage effects in duo-lateral PSDs: Using SEM microscopy and UV beam profiling techniques
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There has been an increase in the use of duo‐lateral position sensitive detectors inpractically every radiation and beam detection application. These devices unlike other light detection system utilize the effect of the lateral division of the generated photocurrent to measure the position of the integral focus of an incoming lightsignal. The performance of a PSD is impaired or strengthened by a number of events caused by parameters such as interface states and recombination introduced during the fabrication of the detector and/or its absorption of ionizing particles. This thesis show the results from the successful implementation of alternative characterization methods of these effects and parameters using scanning electronmicroscopy and UV beam profiling techniques on duo‐lateral position sensitive detectors (LPSDs). To help create the groundwork for the research content of this thesis, different technical reviews of previous studies on interface states, surface recombination velocity and radiation damage due to continuous absorption of ionizing irradiation on detectors are investigated. The thesis also examines published theoretical and measurement techniques used to characterize these surface/interface phenomena. The PSDs used in this research were developed using silicon technology and the various methodologies put into the fabrication of the detectors (n+p and p+n structures) were fashioned after the simulated models. The various steps associated with the clean room fabrication and the prior simulation steps are highlighted in the content of the thesis. Also discussed are the measurement techniques used incharacterizing the fixed oxide charge, surface recombination and the position deviation error of the LPSDs in a high vacuum environment of a scanning electron microscope SEM chamber. Using this method, the effects of interface states and surface recombination velocity on the responsivity of differently doped LPSDs were investigated. By lithographically patterning grid‐like structures used as scaleon n+p doped LPSD and using sweeping electrons from the SEM microscope, a very high linearity over the two‐dimensions of the LPSD total active area was observed. An improved responsivity for low energetic electrons was also achievedby the introduced n+p structure. The lithographically patterned grids helped eliminate further external measurement errors and uncertainties from the use of other typical movable measurement devices such as actuators and two dimensional adjusters which would normally be difficult to install in a remote vacuum chamber. In a similar vein, field plate and field rings were patterned around an array ofthe PSDs used as pixel detector(s). By studying the interpixel resistance and breakdown characteristics, the most effective structural arrangement of the field plate and field rings used to curb induced inversion channel between the n+ doped regions of the pixel‐detector is observed. By using UV beam profiling after the irradiation of UV (193 nm or 253 nm) beam on n+p and p+n doped PSDs, the degree of radiation damage was also investigated. The results obtained help to illustrate how prolonged UV radiation can impact on the linearity and the position deviation/error of UV detectors. The results in this thesis are most relevant in spectroscopic and microscopic applications where low energy electrons and medium UV (MUV) radiation are used.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2014. , 88 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 195
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-22221Local ID: STCISBN: 978-91-87557-71-2 (print)OAI: oai:DiVA.org:miun-22221DiVA: diva2:726925
Public defence
2014-06-17, 10:30 (English)
Supervisors
Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-03-06Bibliographically approved
List of papers
1. High resolution, low energy electron detector
Open this publication in new window or tab >>High resolution, low energy electron detector
2011 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 6, no 1, Art. no. P01001- p.Article in journal (Refereed) Published
Abstract [en]

Electron detection at low energy range for scanning electron microscope (SEM), electron capture detector and electron probe micro-analysis (EPMA) applications, require detectors with high sensitivity and accuracy for low energy range. Such detectors must therefore have a thin entrance window and low recombination at the Si-SiO2 interface. An electron detector with 100 photons to electron-hole pair production rate having a 10 nm SiO2 passivating layer reveals a responsivity of approximately 0.25 A/W when irradiated. Simulations results showing the responsivity of electron interaction between detectors of varied interface fixed oxide charge density Qf show that there is an appreciable difference with the responsivity of a p +n detector and that of an n+p. The simulation results also show the significance of the effect of the minority carriers transport velocity Sn,p on the responsivity of the detector. © 2011 IOP Publishing Ltd and SISSA.

Keyword
Detector modelling and simulations II (electric fields, charge transport, multiplication and induction, pulse formation, electron emission, etc), Interaction of radiation with matter, Solid state detectors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-14219 (URN)10.1088/1748-0221/6/01/P01001 (DOI)000291345600001 ()2-s2.0-79952836489 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2011-07-19 Created: 2011-07-19 Last updated: 2017-12-08Bibliographically approved
2. Surface State Effects on N+P Doped Electron Detector
Open this publication in new window or tab >>Surface State Effects on N+P Doped Electron Detector
2011 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 6, no 12, Art. no. C12019- p.Article in journal (Refereed) Published
Abstract [en]

Surface states and interface recombination velocity that exist between detector interfaces have always been known to affect the performance of a detector. This article describes how the detector performance varies when the doping profile is altered. When irradiated with electrons, the results show that while changes in the doping profile have an effect of the detector responsivity with respect to the interface recombination velocity

Vs, there is no visible effect with respect tofixed oxide charge

Qfotherwise known as interface fixed charge density.

Keyword
Interaction of radiation with matter; Detector modelling and simulations II (electric fields, charge transport, multiplication and induction, pulse formation, electron emission
National Category
Nano Technology
Identifiers
urn:nbn:se:miun:diva-15251 (URN)10.1088/1748-0221/6/12/C12019 (DOI)000299536600019 ()2-s2.0-84855426427 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Conference
13th INTERNATIONAL WORKSHOP ON RADIATION IMAGING DETECTORS, 3–7 JULY 2011, ETH ZURICH, SWITZERLAND
Note

13th INTERNATIONAL WORKSHOP ON RADIATION IMAGING DETECTORS, 3–7 JULY 2011, ETH ZURICH, SWITZERLAND

Available from: 2011-12-14 Created: 2011-12-14 Last updated: 2017-12-08Bibliographically approved
3. A Different Approach of Determining the Responsivity of n+p Detectors Using Scanning Electron Microscopy
Open this publication in new window or tab >>A Different Approach of Determining the Responsivity of n+p Detectors Using Scanning Electron Microscopy
2012 (English)In: Journal of semiconductors, ISSN 1674-4926, Vol. 33, no 7, 074002- p.Article in journal (Refereed) Published
Abstract [en]

This paper explores an alternative to the standard method of studying the responsivities (the input—output gain) and other behaviours of detectors at low electron energy. The research does not aim to compare the results of differently doped n+p detectors; its purpose is to provide an alternative characterization method (using scanning electron microscopy) to those used in previous studies on the responsivity of n+p doped detectors as a function of the electron radiation energy and other interface parameters.

Keyword
Condensed matter: electrical, magnetic and optical, Electronics and devices, Semiconductors, Surfaces, interfaces and thin films, Optics, quantum optics and lasers
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-17237 (URN)10.1088/1674-4926/33/7/074002 (DOI)2-s2.0-84864227940 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2012-10-25 Created: 2012-10-25 Last updated: 2017-06-30Bibliographically approved
4. N+P photodetector characterization using the quasi-steady state photoconductance decay method
Open this publication in new window or tab >>N+P photodetector characterization using the quasi-steady state photoconductance decay method
2012 (English)In: Journal of Semiconductors, ISSN 1674-4926, Vol. 33, no 12, Art. no. 123002- p.Article in journal (Refereed) Published
Abstract [en]

When a material is irradiated, it becomes more electrically conductive due to the absorption of the electromagnetic radiation. As a result, the number of free electrons and holes changes and raises its electrical conductivity. A simple but interesting phenomenon to characterise a fabricated n+p photodetector in order to determine its linearity (photoresponse) and photoconductance was employed. Using the transient decay when the irradiation source is switched off, the minority carrier concentration, effective lifetime and surface recombination velocity present at the surface of the detector were measured. © 2012 Chinese Institute of Electronics.

Keyword
minority carrier lifetime, photoconductance decay, photodetector characterization, surface recombination velocity
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-18298 (URN)10.1088/1674-4926/33/12/123002 (DOI)2-s2.0-84871375183 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Note

Language of Original Document: English

Available from: 2013-01-16 Created: 2013-01-16 Last updated: 2016-10-20Bibliographically approved
5. Simulation and measurement of short infrared pulses on silicon position sensitive device
Open this publication in new window or tab >>Simulation and measurement of short infrared pulses on silicon position sensitive device
2011 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 6, no C01036Article in journal (Refereed) Published
Abstract [en]

Lateral position sensitive devices (PSD) are important for triangulation, alignment and surface measurements as well as for angle measurements. Large PSDs show a delay on rising and falling edges when irradiated with near infra-red light [1]. This delay is also dependent on the spot position relative to the electrodes. It is however desirable in most applications to have a fast response. We investigated the responsiveness of a Sitek PSD in a mixed mode simulation of a two dimensional full sized detector. For simulation and measurement purposes focused light pulses with awavelength of 850 nm, duration of 1 µs and spot size of 280 µm were used. The cause for the slopes of rise and fall time is due to time constants of the device capacitance as well as the photo- generation mechanism itself [1]. To support the simulated results, we conducted measurements of rise and fall times on a physical device. Additionally, we quantified the homogeneity of the device by repositioning a spot of light from a pulsed ir-laser diode on the surface area.

Keyword
Solid state detectors; Detector modelling and simulations II (electric fields, charge, transport, multiplication and induction, pulse formation, electron emission, etc); Photon detectors for UV, visible and IR photons (solid-state)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-13153 (URN)10.1088/1748-0221/6/01/C01036 (DOI)000291345600041 ()STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2011-01-24 Created: 2011-01-24 Last updated: 2017-12-11Bibliographically approved
6. Gridded Duo-lateral Position Sensitivity Detector with High Linearity to Low Energetic Electrons in Vacuum Environment
Open this publication in new window or tab >>Gridded Duo-lateral Position Sensitivity Detector with High Linearity to Low Energetic Electrons in Vacuum Environment
2014 (English)In: IET Optoelectronics, ISSN 1751-8768, E-ISSN 1751-8776, Vol. 8, no 6, 217-225 p.Article in journal (Refereed) Published
Abstract [en]

Characterizing a position sensitive detector in a vacuum environment without beam position monitoring devices can bechallenging and expensive. With this in mind, we have designed and fabricated a duo-lateral position sensitive detector (PSD) incorporatedwith simple and inexpensive surface features. It was evaluated using scanning electron microscopy. To assist in pinpointing precise positioningas well as acting as path guide during the sweeping of electrons, multiple grids were lithographically patterned on the top layer of the duolateralPSD. By sweeping electrons along two axes of the detector, the position detection error of both axes was determined from the signalsrecorded using a transimpedance amplification circuit. We were able to characterize the linearity over the x- and y-axis of the PSD and theresults show a very high linearity over two-dimensions of the PSD’s active area and that accurate beam monitoring for spectroscopic measurement without additional beam position monitoring devices is possible.

Keyword
position sensitive particle detectors, scanning electron microscopy, gridded duo-lateral position sensitivity detector, high linearity, low energetic electrons, vacuum environment, scanning electron microscopy, lithographically patterned multiple grids, position detection error, transimpedance amplification circuit, spectroscopic measurement
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-22223 (URN)10.1049/iet-opt.2014.0002 (DOI)000345689300004 ()2-s2.0-84918795696 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-12-05Bibliographically approved
7. Fabrication, Characterization and Simulation of Channel Stop for n in p-Substrate Silicon Pixel Detectors
Open this publication in new window or tab >>Fabrication, Characterization and Simulation of Channel Stop for n in p-Substrate Silicon Pixel Detectors
Show others...
2014 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, no 7, Art. no. C07013- p.Article in journal (Refereed) Published
Abstract [en]

Silicon detectors made on p-substrates are expected to have a better radiation hardness as compared todetectors made on n-substrates. However, the fixed positive oxide charges induce an inversion layer ofelectrons in the substrate, which connects the pixels. The common means of solving this problem isby using a p-spray, individual p-stops or a combination of the two. Here, we investigate the use offield plates to suppress the fixed positive charges and to prevent the formation of an inversion layer.The fabricated detector shows a high breakdown voltage and low interpixel leakage current for astructure using biased field plates with a width of 20 μm. By using a spice model for simulation of thepreamplifier, a cross talk of about 1.6 % is achieved with this detector structure. The cross talk iscaused by capacitive and resistive coupling between the pixels

Keyword
Electronic detector readout concepts (solid-state), Radiation-hard detectors, Solid state detectors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-22224 (URN)10.1088/1748-0221/9/07/C07013 (DOI)000340050700013 ()2-s2.0-84905165594 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-12-05Bibliographically approved
8. Comparative Study of UV Radiation Hardness of n+p and p+n Duo-Lateral Position Sensitive Detectors
Open this publication in new window or tab >>Comparative Study of UV Radiation Hardness of n+p and p+n Duo-Lateral Position Sensitive Detectors
2014 (English)In: European Physical Journal: Applied physics, ISSN 1286-0042, E-ISSN 1286-0050, Vol. 68, no 2, Art. no. 21301- p.Article in journal (Refereed) Published
Abstract [en]

We report experimental results on the degree of radiation damage in two duo-lateral position sensitive detectors (LPSDs) exposed to 193 nm and253 nm ultraviolet (UV) beam. One of the detectors was an in-house fabricated n(+) p LPSD and the other was a commercially available p(+) n LPSD. We report that at both wavelengths, the degradation damage from the UV photons absorption caused a much more significant deterioration in responsivity in the p(+) n LPSD than in the n(+) p LPSD. By employing a simple method, we were able to visualize the radiation damage on the active area of the LPSDs using 3-dimensional graphs. We were also able to characterize the impact of radiation damage on the linearity and position error of the detectors.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-22226 (URN)10.1051/epjap/2014140253 (DOI)000344614900010 ()2-s2.0-84908010170 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-12-05Bibliographically approved

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Esebamen, Omeime Xerviar

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