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Special Issue "Photodetectors"

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A special issue of Sensors (ISSN 1424-8220).

Deadline for manuscript submissions: closed (31 May 2013)

Special Issue Editor

Guest Editor
Prof. Dr. Bahram Nabet (Website)

Electrical and Computer Engineering Department, College of Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104-2875, USA
Phone: +1 215 895 6761
Interests: optoelectronic devices and systems; reduced dimensional systems and their use in high-speed low-noise sensors of light, charged particles, and TeraHertz radiation

Special Issue Information

Dear Colleagues,

The special issue on photodetectors intends to cover state of the art in detection of light, broadened to include electromagnetic radiation such as x-ray and THz radiation, as well as particle detection. Papers are solicited  which deal with all aspects of absorption of light in different media and structures, generation of carriers or other forms of interaction of light with the medium, such as plasmon resonance, and transport, collection, and generation of electric signal resulting from this optical excitation. Of special interest is structures with sub-wavelength dimensions such as quantum dots and wires, two-dimensional systems such as graphene or 2D electron or hole gasses, and arrays of such systems such as photonic bandgap materials. Regular research articles as well as review articles are welcome.

Prof. Dr. Bahram Nabet
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).

Published Papers (12 papers)

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Research

Jump to: Review

Open AccessArticle Identification and Quantification of Explosives in Nanolitre Solution Volumes by Raman Spectroscopy in Suspended Core Optical Fibers
Sensors 2013, 13(10), 13163-13177; doi:10.3390/s131013163
Received: 8 August 2013 / Revised: 18 September 2013 / Accepted: 24 September 2013 / Published: 30 September 2013
Cited by 9 | PDF Full-text (1193 KB) | HTML Full-text | XML Full-text
Abstract
A novel approach for identifying explosive species is reported, using Raman spectroscopy in suspended core optical fibers. Numerical simulations are presented that predict the strength of the observed signal as a function of fiber geometry, with the calculated trends verified experimentally and [...] Read more.
A novel approach for identifying explosive species is reported, using Raman spectroscopy in suspended core optical fibers. Numerical simulations are presented that predict the strength of the observed signal as a function of fiber geometry, with the calculated trends verified experimentally and used to optimize the sensors. This technique is used to identify hydrogen peroxide in water solutions at volumes less than 60 nL and to quantify microgram amounts of material using the solvent’s Raman signature as an internal calibration standard. The same system, without further modifications, is also used to detect 1,4-dinitrobenzene, a model molecule for nitrobenzene-based explosives such as 2,4,6-trinitrotoluene (TNT). Full article
(This article belongs to the Special Issue Photodetectors)
Figures

Open AccessArticle Visible Light Communication System Using an Organic Bulk Heterojunction Photodetector
Sensors 2013, 13(9), 12266-12276; doi:10.3390/s130912266
Received: 1 July 2013 / Revised: 3 September 2013 / Accepted: 9 September 2013 / Published: 12 September 2013
Cited by 12 | PDF Full-text (273 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based [...] Read more.
A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on an organic photodetector having as active layer a blend of poly(3-hexylthiophene) (P3HT) and phenyl C61-butyric acid methyl ester (PCBM). The OPD is opto-electrically characterized, showing a responsivity of 0.18 A/W and a modulation response of 790 kHz at −6 V. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessArticle Currents Induced by Injected Charge in Junction Detectors
Sensors 2013, 13(9), 12295-12328; doi:10.3390/s130912295
Received: 25 July 2013 / Revised: 21 August 2013 / Accepted: 4 September 2013 / Published: 12 September 2013
Cited by 8 | PDF Full-text (907 KB) | HTML Full-text | XML Full-text
Abstract
The problem of drifting charge-induced currents is considered in order to predict the pulsed operational characteristics in photo-and particle-detectors with a junction controlled active area. The direct analysis of the field changes induced by drifting charge in the abrupt junction devices with [...] Read more.
The problem of drifting charge-induced currents is considered in order to predict the pulsed operational characteristics in photo-and particle-detectors with a junction controlled active area. The direct analysis of the field changes induced by drifting charge in the abrupt junction devices with a plane-parallel geometry of finite area electrodes is presented. The problem is solved using the one-dimensional approach. The models of the formation of the induced pulsed currents have been analyzed for the regimes of partial and full depletion. The obtained solutions for the current density contain expressions of a velocity field dependence on the applied voltage, location of the injected surface charge domain and carrier capture parameters. The drift component of this current coincides with Ramo’s expression. It has been illustrated, that the synchronous action of carrier drift, trapping, generation and diffusion can lead to a vast variety of possible current pulse waveforms. Experimental illustrations of the current pulse variations determined by either the rather small or large carrier density within the photo-injected charge domain are presented, based on a study of Si detectors. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessArticle Theoretical Analysis of Interferometer Wave Front Tilt and Fringe Radiant Flux on a Rectangular Photodetector
Sensors 2013, 13(9), 11861-11898; doi:10.3390/s130911861
Received: 5 August 2013 / Revised: 26 August 2013 / Accepted: 4 September 2013 / Published: 6 September 2013
PDF Full-text (3026 KB) | HTML Full-text | XML Full-text
Abstract
This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where [...] Read more.
This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where these opto-electronic devices are employed for partial fringe counting. Formulas are derived for radiant flux across the detector for variable location within the fringe pattern and with varying wave front angle. The results indicate that the flux is a damped sine function of the wave front angle, with a decay constant of the ratio of wavelength to detector width. The modulation amplitude of the dynamic fringe pattern reduces to zero at wave front angles that are an integer multiple of this ratio and the results show that the polarity of the radiant flux changes exclusively at these multiples. Varying tilt angle causes radiant flux oscillations under an envelope curve, the frequency of which is dependent on the location of the detector with the fringe pattern. It is also shown that a fringe count of zero can be obtained for specific photodetector locations and wave front angles where the combined effect of fringe contraction and fringe tilt can have equal and opposite effects. Fringe tilt as a result of a wave front angle of 0.05° can introduce a phase measurement difference of 16° between a photodetector/pixel located 20 mm and one located 100 mm from the optical origin. Full article
(This article belongs to the Special Issue Photodetectors)
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Open AccessArticle A Comparative Analysis between Active and Passive Techniques for Underwater 3D Reconstruction of Close-Range Objects
Sensors 2013, 13(8), 11007-11031; doi:10.3390/s130811007
Received: 9 July 2013 / Revised: 2 August 2013 / Accepted: 2 August 2013 / Published: 20 August 2013
Cited by 13 | PDF Full-text (1218 KB) | HTML Full-text | XML Full-text
Abstract
In some application fields, such as underwater archaeology or marine biology, there is the need to collect three-dimensional, close-range data from objects that cannot be removed from their site. In particular, 3D imaging techniques are widely employed for close-range acquisitions in underwater [...] Read more.
In some application fields, such as underwater archaeology or marine biology, there is the need to collect three-dimensional, close-range data from objects that cannot be removed from their site. In particular, 3D imaging techniques are widely employed for close-range acquisitions in underwater environment. In this work we have compared in water two 3D imaging techniques based on active and passive approaches, respectively, and whole-field acquisition. The comparison is performed under poor visibility conditions, produced in the laboratory by suspending different quantities of clay in a water tank. For a fair comparison, a stereo configuration has been adopted for both the techniques, using the same setup, working distance, calibration, and objects. At the moment, the proposed setup is not suitable for real world applications, but it allowed us to conduct a preliminary analysis on the performances of the two techniques and to understand their capability to acquire 3D points in presence of turbidity. The performances have been evaluated in terms of accuracy and density of the acquired 3D points. Our results can be used as a reference for further comparisons in the analysis of other 3D techniques and algorithms. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessArticle A Phenomenological Model for the Photocurrent Transient Relaxation Observed in ZnO-Based Photodetector Devices
Sensors 2013, 13(8), 9921-9940; doi:10.3390/s130809921
Received: 31 May 2013 / Revised: 26 July 2013 / Accepted: 29 July 2013 / Published: 5 August 2013
Cited by 15 | PDF Full-text (510 KB) | HTML Full-text | XML Full-text
Abstract
We present a phenomenological model for the photocurrent transient relaxation observed in ZnO-based metal-semiconductor-metal (MSM) planar photodetector devices based on time-resolved surface band bending. Surface band bending decreases during illumination, due to migration of photogenerated holes to the surface. Immediately after turning [...] Read more.
We present a phenomenological model for the photocurrent transient relaxation observed in ZnO-based metal-semiconductor-metal (MSM) planar photodetector devices based on time-resolved surface band bending. Surface band bending decreases during illumination, due to migration of photogenerated holes to the surface. Immediately after turning off illumination, conduction-band electrons must overcome a relatively low energy barrier to recombine with photogenerated holes at the surface; however, with increasing time, the adsorption of oxygen at the surface or electron trapping in the depletion region increases band bending, resulting in an increased bulk/surface energy barrier that slows the transport of photogenerated electrons. We present a complex rate equation based on thermionic transition of charge carriers to and from the surface and numerically fit this model to transient photocurrent measurements of several MSM planar ZnO photodetectors at variable temperature. Fitting parameters are found to be consistent with measured values in the literature. An understanding of the mechanism for persistent photoconductivity could lead to mitigation in future device applications. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessArticle Electric Field and Current Transport Mechanisms in Schottky CdTe X-ray Detectors under Perturbing Optical Radiation
Sensors 2013, 13(7), 9414-9434; doi:10.3390/s130709414
Received: 28 May 2013 / Revised: 12 July 2013 / Accepted: 19 July 2013 / Published: 22 July 2013
Cited by 3 | PDF Full-text (872 KB) | HTML Full-text | XML Full-text
Abstract
Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is [...] Read more.
Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden. Full article
(This article belongs to the Special Issue Photodetectors)
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Open AccessArticle Photo-Detectors Integrated with Resonant Tunneling Diodes
Sensors 2013, 13(7), 9464-9482; doi:10.3390/s130709464
Received: 14 June 2013 / Revised: 9 July 2013 / Accepted: 16 July 2013 / Published: 22 July 2013
Cited by 6 | PDF Full-text (1873 KB) | HTML Full-text | XML Full-text
Abstract
We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the [...] Read more.
We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD’s NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessArticle Performance Enhancement of a GaAs Detector with a Vertical Field and an Embedded Thin Low-Temperature Grown Layer
Sensors 2013, 13(2), 2475-2483; doi:10.3390/s130202475
Received: 17 December 2012 / Revised: 6 February 2013 / Accepted: 8 February 2013 / Published: 18 February 2013
Cited by 2 | PDF Full-text (432 KB) | HTML Full-text | XML Full-text
Abstract
Low temperature growth of GaAs (LT-GaAs) near 200 °C results in a recombination lifetime of nearly 1 ps, compared with approximately 1 ns for regular temperature ~600 °C grown GaAs (RT-GaAs), making it suitable for ultra high speed detection applications. However, LT-GaAs [...] Read more.
Low temperature growth of GaAs (LT-GaAs) near 200 °C results in a recombination lifetime of nearly 1 ps, compared with approximately 1 ns for regular temperature ~600 °C grown GaAs (RT-GaAs), making it suitable for ultra high speed detection applications. However, LT-GaAs detectors usually suffer from low responsivity due to low carrier mobility. Here we report electro-optic sampling time response measurements of a detector that employs an AlGaAs heterojunction, a thin layer of LT-GaAs, a channel of RT-GaAs, and a vertical electric field that together facilitate collection of optically generated electrons while suppressing collection of lower mobility holes. Consequently, these devices have detection efficiency near that of RT-GaAs yet provide pulse widths nearly an order of magnitude faster—~6 ps for a cathode-anode separation of 1.3 μm and ~12 ps for distances more than 3 μm. Full article
(This article belongs to the Special Issue Photodetectors)

Review

Jump to: Research

Open AccessReview Development of an Amorphous Selenium-Based Photodetector Driven by a Diamond Cold Cathode
Sensors 2013, 13(10), 13744-13778; doi:10.3390/s131013744
Received: 19 August 2013 / Revised: 12 September 2013 / Accepted: 23 September 2013 / Published: 11 October 2013
Cited by 4 | PDF Full-text (1896 KB) | HTML Full-text | XML Full-text
Abstract
Amorphous-selenium (a-Se) based photodetectors are promising candidates for imaging devices, due to their high spatial resolution and response speed, as well as extremely high sensitivity enhanced by an internal carrier multiplication. In addition, a-Se is reported to show sensitivity against wide variety [...] Read more.
Amorphous-selenium (a-Se) based photodetectors are promising candidates for imaging devices, due to their high spatial resolution and response speed, as well as extremely high sensitivity enhanced by an internal carrier multiplication. In addition, a-Se is reported to show sensitivity against wide variety of wavelengths, including visible, UV and X-ray, where a-Se based flat-panel X-ray detector was proposed. In order to develop an ultra high-sensitivity photodetector with a wide detectable wavelength range, a photodetector was fabricated using a-Se photoconductor and a nitrogen-doped diamond cold cathode. In the study, a prototype photodetector has been developed, and its response to visible and ultraviolet light are characterized. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessReview A Comprehensive Review of Semiconductor Ultraviolet Photodetectors: From Thin Film to One-Dimensional Nanostructures
Sensors 2013, 13(8), 10482-10518; doi:10.3390/s130810482
Received: 17 June 2013 / Revised: 2 August 2013 / Accepted: 8 August 2013 / Published: 13 August 2013
Cited by 88 | PDF Full-text (1229 KB) | HTML Full-text | XML Full-text
Abstract
Ultraviolet (UV) photodetectors have drawn extensive attention owing to their applications in industrial, environmental and even biological fields. Compared to UV-enhanced Si photodetectors, a new generation of wide bandgap semiconductors, such as (Al, In) GaN, diamond, and SiC, have the advantages of [...] Read more.
Ultraviolet (UV) photodetectors have drawn extensive attention owing to their applications in industrial, environmental and even biological fields. Compared to UV-enhanced Si photodetectors, a new generation of wide bandgap semiconductors, such as (Al, In) GaN, diamond, and SiC, have the advantages of high responsivity, high thermal stability, robust radiation hardness and high response speed. On the other hand, one-dimensional (1D) nanostructure semiconductors with a wide bandgap, such as β-Ga2O3, GaN, ZnO, or other metal-oxide nanostructures, also show their potential for high-efficiency UV photodetection. In some cases such as flame detection, high-temperature thermally stable detectors with high performance are required. This article provides a comprehensive review on the state-of-the-art research activities in the UV photodetection field, including not only semiconductor thin films, but also 1D nanostructured materials, which are attracting more and more attention in the detection field. A special focus is given on the thermal stability of the developed devices, which is one of the key characteristics for the real applications. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessReview Progress in Infrared Photodetectors Since 2000
Sensors 2013, 13(4), 5054-5098; doi:10.3390/s130405054
Received: 23 January 2013 / Revised: 3 April 2013 / Accepted: 9 April 2013 / Published: 16 April 2013
Cited by 32 | PDF Full-text (701 KB) | HTML Full-text | XML Full-text
Abstract
The first decade of the 21st-century has seen a rapid development in infrared photodetector technology. At the end of the last millennium there were two dominant IR systems, InSb- and HgCdTe-based detectors, which were well developed and available in commercial systems. While [...] Read more.
The first decade of the 21st-century has seen a rapid development in infrared photodetector technology. At the end of the last millennium there were two dominant IR systems, InSb- and HgCdTe-based detectors, which were well developed and available in commercial systems. While these two systems saw improvements over the last twelve years, their change has not nearly been as marked as that of the quantum-based detectors (i.e., QWIPs, QDIPs, DWELL-IPs, and SLS-based photodetectors). In this paper, we review the progress made in all of these systems over the last decade plus, compare the relative merits of the systems as they stand now, and discuss where some of the leading research groups in these fields are going to take these technologies in the years to come. Full article
(This article belongs to the Special Issue Photodetectors)

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