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Photodetectors
Kinds of Photodetectors Selected AbstractsGaN Nanofibers based on Electrospinning: Facile Synthesis, Controlled Assembly, Precise Doping, and Application as High Performance UV Photodetector,ADVANCED MATERIALS, Issue 2 2009Hui Wu Nitride nanofibers have been synthesized based on a simple electrospinning technique for the first time. No catalysts or templates are needed in this new synthetic method. Highly oriented GaN nanofiber arrays, as well as a high-performance UV photodetector based on single GaN nanofiber assembled FET devices, can be facilely fabricated using this technique. Precise doping of other elements into the GaN nanofibers is easy by this solution-based synthetic method. [source] Organic Electronic Interface Devices: Light- and Touch-Point Localization using Flexible Large Area Organic Photodiodes and Elastomer Waveguides (Adv. Mater.ADVANCED MATERIALS, Issue 34 200934/2009) The inside cover shows a flexible, large-area, position-sensitive organic photodetector used as an input device for a desktop computer. R. Koeppe et al. show the assembly of such a device with a photodiode based on a blend of Zn-phthalocyanine and C60 with low conductivity electrodes on p. 3510. The current drop across the electrodes easily allows for the calculation of the position of a localized light signal impinging on the position-sensitive photodetector. By adding an additional elastomer layer with embedded LEDs, the device can also be used as flexible touchpad. [source] GaN Nanofibers based on Electrospinning: Facile Synthesis, Controlled Assembly, Precise Doping, and Application as High Performance UV Photodetector,ADVANCED MATERIALS, Issue 2 2009Hui Wu Nitride nanofibers have been synthesized based on a simple electrospinning technique for the first time. No catalysts or templates are needed in this new synthetic method. Highly oriented GaN nanofiber arrays, as well as a high-performance UV photodetector based on single GaN nanofiber assembled FET devices, can be facilely fabricated using this technique. Precise doping of other elements into the GaN nanofibers is easy by this solution-based synthetic method. [source] Charge-injection photogate pixel fabricated in CMOS silicon-on-insulator technologyINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 2 2009Daniel Durini Abstract Concept, theoretical analysis, and experimental results obtained from a charge-injection photogate (CI-PG) pixel detector fabricated in CMOS silicon-on-insulator (SOI) technology are presented. The charge collected in the photodetector during a certain charge collection (integration) time is injected into the substrate for readout. This readout principle presents a huge internal photocurrent amplification (,104) taking place in the photodetector, obtained through the ,time-compression' approach. Here, the readout circuitry is fabricated on highly doped, 200,nm thick, SOI film, while the photogate detector is fabricated on higher resistivity handle-wafer. The latter, together with the 30,V biasing possibilities, enhances the quantum efficiency of the pixel, especially for irradiations with wavelengths in the near-infra-red part of the spectra. Copyright © 2008 John Wiley & Sons, Ltd. [source] Genetic, Temporal and Developmental Differences Between Melatonin Rhythm Generating Systems in the Teleost Fish Pineal Organ and RetinaJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2003J. Falcón Abstract Complete melatonin rhythm generating systems, including photodetector, circadian clock and melatonin synthesis machinery, are located within individual photoreceptor cells in two sites in Teleost fish: the pineal organ and retina. In both, light regulates daily variations in melatonin secretion by controlling the activity of arylalkylamine N -acetyltransferase (AANAT). However, in each species examined to date, marked differences exist between the two organs which may involve the genes encoding the photopigments, genes encoding AANAT, the times of day at which AANAT activity and melatonin production peak and the developmental schedule. We review the fish pineal and retinal melatonin rhythm generating systems and consider the evolutional pressures and other factors which led to these differences. [source] Microwave signal generation based on two single-longitudinal-mode erbium-doped fiber lasersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2010Jian-Hua Luo Abstract A simple microwave signal source is proposed by connecting two single-longitudinal-mode erbium-doped distributed Bragg reflector fiber lasers in series. For using same pump LD, mutual injection locking of two fiber lasers is achieved. The two single-longitudinal-mode lasers have 0.048 nm wavelength difference. By beating the two wavelengths at a photodetector, stable microwave signal at 6.17 GHz is achieved at room temperature. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 177,179, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24840 [source] Microwave characteristics of substrate integrated waveguide photodetectorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009Ebrahim Mortazy Abstract In this article, using a novel structure, simulated and measured microwave characteristics from substrate integrated waveguide photodetector (SIWPD) are obtained and compared with the conventional microstrip waveguide photodetector. A Ka-band microstrip to rectangular waveguide multilayer transition for OC-768/STM-256 optical systems is designed and fabricated. Attenuation constant results shows that by replacing substrate integrated waveguide (SIW) instead of conventional microstrip in waveguide photodetectors, operation frequency can be increased. Microwave fields in the proposed structure show a good transition from quasi-TEM mode to TE10 mode in multilayer structure. The multilayer structure is considered to separate SIW and DC bias of the photodetector. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2204,2207, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24528 [source] A CMOS opto-electronic single chip using the hybrid scheme for optical receiversMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2008Jian-Ming Huang Abstract An opto-electronic integrated circuit based on the hybrid scheme for an optical receiver front-end is presented in this article. The proposed integrated circuit adopts the CMOS technology as the vehicle to integrate the InP-based waveguide photodetector into the transimpedance amplifier (TIA) circuit. A regulated cascade structure is used to reduce the input impedance of the TIA. Hence, the proposed integrated circuit can achieve a very high bandwidth provided that the parasitic capacitance of the photodetector is up to 1 pF. The 3-dB bandwidth and the transimpedance gain of the proposed circuit are 1 GHz and 64.5 dB,, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2430,2434, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23693 [source] 1.55-,m surface-illuminated monolithically integrated balanced metal semiconductor metal photodetectors and coplanar waveguideMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2002Amr M. E. Safwat Abstract Two metal,semiconductor,metal (MSM) photodetectors are integrated monolithically with a coplanar waveguide transmission line to form a 1.55-,m surface-illuminated balanced photodetector. Illuminating the device with CW and taking the difference, the relative intensity noise (RIN) is suppressed by 9,10 dB. In balanced detection, a 7-dB enhancement in the intermodulation term compared to single detector is achieved. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 125,130, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10393 [source] ZnO-based photodetector with internal photocurrent gainPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010L. A. Kosyachenko Abstract The photoresponsive structures prepared by magnetron sputtering of ZnO on p-Si substrates followed by vacuum evaporation of semitransparent Ni film on ZnO surface are investigated. The obtained Ni/n-ZnO/p-Si structures show high sensitivity that sharply increases with increase in applied voltage. Under a bias voltage of 5,V, the responsivities at ,,=,390,nm and ,,=,850,nm were equal to 210 and 110,A/W, which correspond to quantum efficiencies of 655 and 165, respectively. It is assumed that the observed strong response is attributed to internal gain in the Ni/n-ZnO/p-Si phototransistor structure containing Ni/n-ZnO Schottky contact as the emitter junction and n-ZnO/p-Si heterostructure as the collector junction. The response time of the device is ,10,7,s. Alternative mechanisms of photocurrent multiplication in such structures are also discussed. [source] All-organic optocouplers based on polymer light-emitting diodes and photodetectorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008N. A. Stathopoulos Abstract In this work, we demonstrate all organic flexible polymeric optocouplers by utilizing a donor-acceptor bulk heterojunction polymer photodetector (PD) as the output unit and a polymer light-emitting diode (PLED) as the input unit. The input unit is a single-layer PLED on a glass or a plastic (PET) substrate utilizing a green emitting polyfluorene-benzothiadiazole copolymer in the active layer. The output unit is a single-layer PD on a glass substrate utilizing a P3HT:PCBM(1:1 by weight) blend, where P3HT is regioregular poly(3-hexylthiophene) and PCBM is (6,6)-phenyl-C61 -butyric acid methyl ester. The electroluminescence spectrum of the PLED peaks at 530 nm and covers a spectral range that coincides quite well with the PD absorption spectrum (between 450 and 650 nm). The current density transfer ratio reaches 0.012% for an optocoupler that operates at 0 V and 15 V for the PD and PLED, respectively. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Si-doped GaN/AlN quantum dot superlattices for optoelectronics at telecommunication wavelengthsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006F. Guillot Abstract We report on the controlled growth of Si doped GaN/AlN quantum dot (QD) superlattices, in order to tailor their intersubband absorption within the 1.3,1.5 µm telecommunication wavelengths. The QD size is tuned by modifying the amount of GaN in the QDs and the growth temperature. Silicon can be incorporated in the QDs to populate the first electronic level, without significant perturbation of the QD morphology. As a proof of the capability of these structures for infrared detection, a quantum-dot intersubband photodetector at 1.38 µm with lateral carrier transport is demonstrated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of AlGaAs cladding layer on GaInNAs/GaAs MQW p-i-n photodetectorPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Y. F. Chen Abstract The electronic properties of GaInNAs/GaAs multiple-quantum-well (MQW) p-i-n photodetector with AlGaAs cladding layer have been studied. By applying a higher band gap Al0.3Ga0.7As to the photodetector, a substantial reduction in dark current was observed owing to an inherent difficulty for holes to surmount the high potential barrier between MQW and the cladding layer heterojunction under a reverse bias. The dark current obtained was as low as 4.1 pA at -3.5 V for a device with Al0.3Ga0.7As cladding layer as compared to 22 ,A also at -3.5 V for a similar device without the Al0.3Ga0.7As cladding layer. The photo/dark current contrast ratios obtained were 4.2×104 and 11, respectively, for devices with and without an Al0.3Ga0.7As cladding layer at -3.5 V. In addition, peak responsivity of 1 mA/W was measured at around 1150 nm. Two orders of magnitude increase in the rejection ratio were realized between 1150 and 1250 nm at -2.0 V. The GaInNAs/GaAs MQW p-i-n photodetector was demonstrated with the AlGaAs cladding layer potentially providing a higher photo/dark current contrast ratio and higher responsivity rejection ratio. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Parallel bandwidth characteristics calculations for thin avalanche photodiodes on a SGI Origin 2000 supercomputerCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2004Yi Pan Abstract An important factor for high-speed optical communication is the availability of ultrafast and low-noise photodetectors. Among the semiconductor photodetectors that are commonly used in today's long-haul and metro-area fiber-optic systems, avalanche photodiodes (APDs) are often preferred over p - i - n photodiodes due to their internal gain, which significantly improves the receiver sensitivity and alleviates the need for optical pre-amplification. Unfortunately, the random nature of the very process of carrier impact ionization, which generates the gain, is inherently noisy and results in fluctuations not only in the gain but also in the time response. Recently, a theory characterizing the autocorrelation function of APDs has been developed by us which incorporates the dead-space effect, an effect that is very significant in thin, high-performance APDs. The research extends the time-domain analysis of the dead-space multiplication model to compute the autocorrelation function of the APD impulse response. However, the computation requires a large amount of memory space and is very time consuming. In this research, we describe our experiences in parallelizing the code in MPI and OpenMP using CAPTools. Several array partitioning schemes and scheduling policies are implemented and tested. Our results show that the code is scalable up to 64 processors on a SGI Origin 2000 machine and has small average errors. Copyright © 2004 John Wiley & Sons, Ltd. [source] An Efficient Way to Assemble ZnS Nanobelts as Ultraviolet-Light Sensors with Enhanced Photocurrent and StabilityADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Xiaosheng Fang Abstract Although there has been significant progress in the fabrication and performance optimization of one-dimensional nanostructure-based photodetectors, it is still a challenge to develop an effective and low-cost device with high performance characteristics, such as a high photocurrent/dark-current ratio, photocurrent stability, and fast time response. Herein an efficient and low-cost method to achieve high-performance ,visible-blind' microscale ZnS nanobelt-based ultraviolet (UV)-light sensors without using a lithography technique, by increasing the nanobelt surface areas exposed to light, is reported. The devices exhibit about 750 times enhancement of a photocurrent compared with individual nanobelt-based sensors and an ultrafast time response. The photocurrent stability and time response to UV-light do not change significantly when a channel distance is altered from 2 to 100,µm or the sensor environment changes from air to vacuum and different measurement temperatures (60 and 150,°C). The photoelectrical behaviors can be recovered well after returning the measurement conditions to air and room temperature again. The low cost and high performance of the resultant ZnS nanobelt photodetectors guarantee their highest potential for visible-blind UV-light sensors working in the UV-A band. [source] Electrical Transport and High-Performance Photoconductivity in Individual ZrS2 NanobeltsADVANCED MATERIALS, Issue 37 2010Liang Li Individual ZrS2 -nanobelt field-effect transistors were fabricated using a photolithography process. Temperature-dependent electrical transport revealed different electrical conductivity mechanism at different working temperature regions. ZrS2 -nanobelt photodetectors demonstrated a high-performance visible-light photoconductivity. [source] Polythiophene-Fullerene Based Photodetectors: Tuning of Spectral Response and Application in Photoluminescence Based (Bio)Chemical SensorsADVANCED MATERIALS, Issue 37 2010Kanwar S. Nalwa A photoluminescence (PL)-based oxygen and glucose sensor utilizing inorganic or organic light emitting diode as the light source, and polythiophene:fullerene type bulk-heterojunction devices as photodetectors, for both intensity and decay-time based monitoring of the sensing element's PL. The sensing element is based on the oxygen-sensitive dye Pt-octaethylporphyrin embedded in a polystyrene matrix. [source] High-Performance Blue/Ultraviolet-Light-Sensitive ZnSe-Nanobelt PhotodetectorsADVANCED MATERIALS, Issue 48 2009Xiaosheng Fang Single-crystalline zinc selenide (ZnSe) nanobelts were fabricated via the ethylenediamine (en)-assisted ternary solution technique and subsequent thermal treatment. Individual ZnSe nanobelts were assembled into nanoscale devices (see figure), showing a high spectral selectivity and photocurrent/immediate-decay ratio and a fast time response, justifying effective utilization of the ZnSe nanobelts as blue/UV-light-sensitive photodetectors. [source] Single-Crystalline ZnS Nanobelts as Ultraviolet-Light SensorsADVANCED MATERIALS, Issue 20 2009Xiaosheng Fang Single-crystalline ZnS nanobelts with sharp ultraviolet-light emission (,337,nm) at room temperature have been assembled as UV Sensors. The high spectral selectivity, combined with high photosensitivity and fast response time, justifies the effective utilization of the present ZnS nanobelts as "visible-light-blind" UV photodetectors in different areas. [source] Solution-Processable Near-IR Photodetectors Based on Electron Transfer from PbS Nanocrystals to Fullerene DerivativesADVANCED MATERIALS, Issue 6 2009Krisztina Szendrei Nanocrystal/fullerene derivative inorganic,organic hybrid photodetectors exhibiting high detectivity for near-IR wavelengths and a linear power dependence are produced. The ultrafast electron transfer from the PbS crystals to the fullerene opens a new route to obtaining efficient photodetectors that are appealing, cost-effective alternatives to the currently available technology. [source] ZnO Nanofiber Field-Effect Transistor Assembled by ElectrospinningJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008Hui Wu A ZnO nanofiber field-effect transistor (FET) was assembled by electrospinning. Uniform ZnO nanofibers with a diameter of ,70 nm and length over 100 ,m were first synthesized by electrospinning. Using two paralleled electrodes as fiber collectors, we have successfully placed a single ZnO nanofiber on the electrodes, and an FET device was fabricated based on the assembled nanofiber. An electrical transport measurement was conducted on the FET device, showing that ZnO nanofibers are intrinsic n- type semiconductors. The present findings demonstrate that electrospinning can potentially be used as a straightforward and cost-effective means for the assembly of one-dimensional nanostuctures for building integrated nanodevices for various applications, such as transistors, sensors, diodes, and photodetectors. [source] Microwave characteristics of substrate integrated waveguide photodetectorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009Ebrahim Mortazy Abstract In this article, using a novel structure, simulated and measured microwave characteristics from substrate integrated waveguide photodetector (SIWPD) are obtained and compared with the conventional microstrip waveguide photodetector. A Ka-band microstrip to rectangular waveguide multilayer transition for OC-768/STM-256 optical systems is designed and fabricated. Attenuation constant results shows that by replacing substrate integrated waveguide (SIW) instead of conventional microstrip in waveguide photodetectors, operation frequency can be increased. Microwave fields in the proposed structure show a good transition from quasi-TEM mode to TE10 mode in multilayer structure. The multilayer structure is considered to separate SIW and DC bias of the photodetector. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2204,2207, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24528 [source] 1.55-,m surface-illuminated monolithically integrated balanced metal semiconductor metal photodetectors and coplanar waveguideMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2002Amr M. E. Safwat Abstract Two metal,semiconductor,metal (MSM) photodetectors are integrated monolithically with a coplanar waveguide transmission line to form a 1.55-,m surface-illuminated balanced photodetector. Illuminating the device with CW and taking the difference, the relative intensity noise (RIN) is suppressed by 9,10 dB. In balanced detection, a 7-dB enhancement in the intermodulation term compared to single detector is achieved. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 125,130, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10393 [source] Photoluminescence properties of GaAs nanowire ensembles with zincblende and wurtzite crystal structurePHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010B. V. Novikov Abstract Self-standing III,V nanowires (NWs) are promising building blocks for future optoelectronic devices such as LEDs, lasers, photodetectors and solar cells. In this work, we present the results of low temperature photoluminescence (PL) characterization of GaAs NWs grown by Au-assisted molecular beam epitaxy (MBE), coupled with the transmission electron microscopy (TEM) structural analysis. PL spectra contain exci- ton peaks from zincblende (ZB) and wurtzite (WZ) crystal structures of GaAs. The peaks are influenced by the quantum confinement effects. PL bands corresponding to the exciton emission from ZB and WZ crystal phases are identified, relating to the PL peaks at 1.519 eV and 1.478 eV, respectively. The obtained red shift of 41 meV for WZ GaAs should persist in thin NWs as well as in bulk materials. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication study of AlN solar-blind (<280,nm) MSM photodetectors grown by low-temperature depositionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010Meei-Ru Chen Abstract AlN, an important semiconductor with the widest band gap among III-nitrides, was employed to construct solar blind metal,semiconductor,metal photodetectors (MSM-PDs). MSM-PDs were fabricated on AlN epitaxial thin films deposited on GaN/sapphire using a helicon sputtering system at a low temperature of 300,°C. The dark current of the device is as low as 200,fA at 20,V and the photocurrent illuminated by a D2 lamp increases more than two orders of magnitude. The photocurrent increases almost linearly with the incident optical power at the wavelength of 200,nm. The results show that the low temperature grown AlN MSM device is suitable for the application of deep UV detection. [source] All-organic optocouplers based on polymer light-emitting diodes and photodetectorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2008N. A. Stathopoulos Abstract In this work, we demonstrate all organic flexible polymeric optocouplers by utilizing a donor-acceptor bulk heterojunction polymer photodetector (PD) as the output unit and a polymer light-emitting diode (PLED) as the input unit. The input unit is a single-layer PLED on a glass or a plastic (PET) substrate utilizing a green emitting polyfluorene-benzothiadiazole copolymer in the active layer. The output unit is a single-layer PD on a glass substrate utilizing a P3HT:PCBM(1:1 by weight) blend, where P3HT is regioregular poly(3-hexylthiophene) and PCBM is (6,6)-phenyl-C61 -butyric acid methyl ester. The electroluminescence spectrum of the PLED peaks at 530 nm and covers a spectral range that coincides quite well with the PD absorption spectrum (between 450 and 650 nm). The current density transfer ratio reaches 0.012% for an optocoupler that operates at 0 V and 15 V for the PD and PLED, respectively. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High performance Schottky UV detectors (265,100 nm) using n-Al0.5Ga0.5N on AlN epitaxial layerPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003H. Miyake Abstract A high responsivity spectrum in the near ultraviolet (UV) and the vacuum UV (VUV) region was realized using Schottky UV detectors consisting of Al0.5Ga0.5N on an AlN epitaxial layer. The cut-off wavelength of AlGaN UV detectors was 4.7 eV (265 nm), a value that corresponds to the band gap of Al0.5Ga0.5N. The contrast of responsivity between the near UV and the visible was about 104. The GaN Schottky detector hads a high responsivity region in the near-UV from 3.4 to 5.0 eV (250,360 nm), whereas the AlGaN UV detector had a high responsivity in the UV,VUV region from 4.7 to 12.4 eV (100,265 nm). From these results, the fabricated AlGaN-based UV photodetectors can likely be used in detectors for the UV,VUV region. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The performance of AlGaN solar blind UV photodetectors: responsivity and decay timePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006G. Cherkashinin Abstract The responsivity and the decay time of AlGaN solar blind UV-detectors have been studied. The photodetectors have shown a good spectral responsivity in a narrow spectral range (220 < , < 300 nm) and a short time response with the best estimated characteristic time constant of , , 30 ms measured at room temperature. Possible mechanisms responsible for the persistent photoconductivity (PPC) effect in AlxGa1,xN (x = 0.51) are analyzed. A shape of the spectral response as a function of the applied voltage is analyzed in the frameworks of the space-charge limited current model. It has been shown that the main source of PPC is traps above the Fermi level. PPC occurs when the density of free carriers equals the density of the traps. The model attributing PPC to the spatial separation of the photoexcited electrons and holes by the macroscopic potential barrier is not supported by our photocurrent studies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Amorphous silicon based p-i-i-n photodetectors for point-of-care testingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Marc Sämann Abstract Modern medical diagnostics demands point-of-care testing (POCT) systems for quick tests in clinical or out-patient environments. This investigation combines the Reflectometric Interference Spectroscopy (RIfS) with thin film technology for a highly sensitive, direct optical and label-free detection of proteins, e.g. inflammation or cardiovascular markers. Amorphous silicon (a-Si) based thin film photodetectors replace the so far needed spectrometer and permit downsizing of the POCT system. Photodetectors with p-i-i-n structure adjust their spectral sensitivity according to the applied read-out voltage. The use of amorphous silicon carbide in the p-type and the first intrinsic layer enhances the sensitivity through very low dark currents of the photodetectors and enables the adjustment of their absorption characteristics. Integrating the thin film photodetectors on the rear side of the RIfS substrate eliminates optical losses and distortions, as compared to the standard RIfS setup. An integrated Application Specific Integrated Circuit (ASIC) chip performs a current-frequency conversion to accurately detect the photocurrent of up to eight parallel photodetector channels. In addition to the optimization of the photo-detectors, this contribution presents first successful direct optical and label-free RIfS measurements of C-reactive protein (CRP) and D-dimer in buffer solution in physiological relevant concentrations. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Monolithically integrated UV/IR-photodetectors based on an AlN/GaN-based superlattice grown on an AlGaN buffer layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Daniel Hofstetter Abstract In this article, we demonstrate closely spaced, monolithically integrated photodetectors in two largely different wavelength ranges. The epitaxial structure of the devices was grown by plasma-assisted molecular-beam epitaxy on an AlN-on-sapphire template; it consists of a Si-doped AlGaN thin film, and a nearly strain compensated 40 period AlN/GaN superlattice with 1.0 nm thick GaN quantum wells and 2.0 nm thick AlN barriers. The entire structure is covered with an AlGaN cap layer. The superlattice acts as active region for the infrared detector, while the AlGaN buffer layer serves as active area for the ultraviolet detector. While the photovoltaic near-infrared detector has a center wavelength of 1.37 ,m, the photoconductive ultraviolet detector has a long wavelength cutoff at 250 nm. The two detectors could be operated up to room temperature with reasonable sensitivities. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||