Special Issue "Photodetectors"

Guest Editor
Prof. Dr. Bahram Nabet
Electrical and Computer Engineering Department, College of Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104-2875, USA
Website: http://www.ece.drexel.edu/index.php?page=person&person=30
E-Mail: nabet@ece.drexel.edu
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

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

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Marc Currie, Pouya Dianat, Anna Persano, Maria Concetta Martucci, Fabio Quaranta, Adriano Cola and Bahram Nabet Article: 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; in revised form: 6 February 2013 / Accepted: 8 February 2013 / Published: 18 February 2013 Show/Hide Abstract | Download PDF Full-text (432 KB) | Download 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 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.

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Chandler Downs and Thomas E. Vandervelde Review: Progress in Infrared Photodetectors Since 2000 Sensors 2013, 13(4), 5054-5098; doi:10.3390/s130405054 Received: 23 January 2013; in revised form: 3 April 2013 / Accepted: 9 April 2013 / Published: 16 April 2013 Show/Hide Abstract | Download PDF Full-text (701 KB) 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 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.

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Type of Paper: Review
Title: Progress in Infrared Photodetectors Since 2000
Authors: Chandler Downs and Thomas Vandervelde
Affiliation: Renewable Energy and Applied Photonics Lab, Tufts University; E-Mail: Chandler.Downs@tufts.edu
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 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.

Type of Paper: Review
Title: A Comprehensive Review of Semiconductor Ultraviolet Photodetectors: From Film to One-dimensional Nanostructures
Authors: Liwen Sang ^1,2, Meiyong Liao ³, and Masatomo Sumiya ^3,4
Affiliations: ¹ International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; E-Mail: SANG.Liwen@nims.go.jp
² JST-PRESTO, the Japan Science and Technology Agency, Tokyo, 102-0076, Japan
³ Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS) Tsukuba, Ibaraki 305-0044, Japan
⁴ JST-ALCA, the Japan Science and Technology Agency, Tokyo, 102-0076, Japan
Abstract: Ultraviolet (UV) photodetectors have drawn more and more attention owing to their applications in industrial, military, environmental and even biological fields. In some cases such as flame detection, high-temperature stable detectors with high performance are required. Compared to UV-enhanced Si photodetector, a new generation of wide bandgap semiconductors, such as Al(In)GaN, diamond, SiC, ZnO or ZnSe have the advantage of high responsivity, high thermal stability, radiation hardness and high response speed. On the other hand, one-dimentional (1D) nanostructure semiconductors with a wide bandgap, such as β-Ga₂O₃, ZnO, ZnS, or ZnSe nanowires and nanobelts, also indicate their potential for the high-efficiency UV photodetection. This article provides a comprehensive review on the state-of-the-art research activities in the UV photodetection field, including not only the semiconductor bulk, but also 1D nanostructured materials, which are attracting more and more attention in the UV 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.

Title: Light Receivers Using Optically Controlled Resonant Tunneling Diode Photodetectors
Authors: B. Romeira ¹, J. M. L Figueiredo ¹, L. Pessoa ², H. Salgado ², H. Cantu ³ and C. N. Ironside ³
Affiliations: ¹ Centro de Electrónica, Optoelectrónica e Telecomunicações, Departamento de Física, Universidade do Algarve, 8005-139 Faro, Portugal; E-Mail: bmromeira@ualg.pt
² INESC-TEC Porto, Faculdade de Engenharia, Universidade do Porto, Portugal
³ School of Engineering, University of Glasgow, Glasgow G12 8LT, UK
Abstract: We report on light receivers employing direct optical control of resonant tunneling diode photodetector (RTD-PD) devices consisting of 10-nm thick InGaAs/AlAs double barrier quantum well semiconductor alloys, surrounded by InGaAlAs photoconductive layers. RTD-PDs operate in the 1530 nm to 1565 nm spectral region, and exhibit strong responsivity dependence as a function of the applied bias voltage because of RTD-PD’s nonlinear current-voltage characteristic with a region of negative differential resistance. Taking advantage of these distinctive characteristics, we demonstrate efficient detection of modulated optical carriers using optical injection locking techniques for applications in generation of stable low-phase noise signals, optoelectronic clock recovery circuits, and radio-over-fiber communication links.

Title: Development of Amorphous Selenium Based Photodetector Driven by Diamond Cold Cathode
Authors: T. Masuzawa ¹, I. Saito ¹, M. Onishi ¹, Y. Suzuki ¹, K. Onuki ¹, N. Kato ¹, T. Yamada ², S. Ogawa ³, Y. Takakuwa ³, A. T T Koh ⁴, D. H C Chua ⁴, Y. Mori ⁵, T. Shimosawa ⁶ and K. Okano ¹
Affiliations: ¹ Dept. of Material Science, International Christian University; E-Mail; mtomoaki@nt.icu.ac.jp
² Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST)
³ Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
⁴ Dept. of Materials Science & Engineering, National University of Singapore
⁵ Department of Electrical Engineering, Graduate School of Engineering, Osaka University
⁶ Dept. of Clinical Laboratory, Faculty of Medicine, University of Tokyo
Abstract: Amorphous-selenium (a-Se) based photodetectors are promising candidate 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 wide wave range, a photodetector was fabricated using a-Se photoconductor and nitrogen-doped diamond cold cathode. Throughout the study, a prototype photodetector has been developed, and response to visible and ultraviolet light are characterized.

Type of Paper: Article
Title: One-Dimensional Inorganic Nanostructures Based Ultraviolet Photodetectors
Authors: Wei Tian ^1,2, Tianyou Zhai ¹, Xi Wang ¹, Dmitri Golberg ¹ and Yoshio Bando ^1,2
Affiliations: ¹ International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan; E-Mails: WEI.Tian@nims.go.jp; ZHAI.Tianyou@nims.go.jp
² Department of Nano-Science and Nano-Engineering, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
Abstract: As important members of the optoelectronic device family, ultraviolet (UV) photodetectors show wide applications in environmental and biological researches, sensors, missile launches, and UV irradiation detectors. The interest in developing high performance UV photodetectors has culminated in the realization of one-dimensional (1D) inorganic nanostructures fabricated by a top-down approach. Benefiting from a large surface-to-volume ratio and a Debye length comparable to their small size, 1D inorganic nanostructures are considered as the most promising building blocks for photodetectors with superior sensitivity, high quantum efficiency, and fast response speed. This article reviews the state-of-the-art research activities that focus on the one-dimensional inorganic nanostructures and their UV photodetector applications. It begins with a survey of 1D inorganic nanostructures and the fundamentals of photodetectors, then shows several kinds of remarkable 1D nanostructures and their photoresponse characteristics, such as binary wide-bandgap materials (ZnO, ZnS, SnO2, Ga2O3, WO3, Nb2O5, GaN, AlN) and ternary nanowire/belt (In2Ge2O7, Zn2GeO4, ZnSnO4 et al). Finally, the article concludes with some perspectives and outlook on the future advancements in the field.

Title: A Phenomenological Model for the Persistent Photoconductivity Observed in ZnO-based Photodetector Devices
Authors: J.C. Moore and C.V. Thompson
Affiliation: Department of Chemistry and Physics, Coastal Carolina University, Conway, SC USA; E-Mail: moorejc@coastal.edu
Abstract: We present a phenomenological model of the persistent photoconductivity observed in ZnO-based 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 increases band bending, resulting in an increased bulk/surface energy barrier that slows 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 correspond to directly measured values in the literature. An understanding of the mechanism for persistent photoconductivity could lead to mitigation in future device applications.

Title: Electric Fields and Current Transport Mechanisms in Schottky CdTe X-Ray Detectors under Perturbing Optical Irradiation
Authors: Adriano Cola * and Isabella Farella
Affiliation: Institute for Microelectronics and Microsystems (CNR-IMM), Via Monteroni, 73100 Lecce, Italy; E-Mails: adriano.cola le.imm.cnr.it (A.C.); isabella.farella le.imm.cnr.it (I.F.)
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. With this aim, we analyze the electric field distribution and the current flowing in such detectors both in the dark and under optical perturbations. Our systematic study explores the detector response by varying experimental parameters, such as voltage, temperature, and radiation wavelength. Transient effects under dark are driven by carrier emission from deep levels, giving rise to the so-called bias induced polarization. Cathode and anode irradiation at different wavelengths evidence the crucial role of the contacts, the cathode being ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection becomes effective 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 that are otherwise hidden.