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Please follow the links to view the publication.Solid-state electroluminescence from porous silicon
http://dl-live.theiet.org/content/conferences/10.1049/ic_19961225
In this paper we describe briefly, the historical development of porous silicon electroluminescent (PSEL) devices. Some optical and electrical characteristics of the most efficient CW operated PSEL device reported to date are presented. In order for PSEL devices to realise their promised potential, several key problems remain to be solved. These problems are discussed, and the prospects for overcoming them are considered. To appreciate better this work, some background information on the fabrication and the structural and optical properties of porous silicon is also presented. (6 pages)Luminescent thin film ZnS:Mn prepared by pulsed laser deposition for flat panel display applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950969
A novel method is described for high rate deposition of ZnS:Mn luminescent thin films by pulsed laser deposition. Good stoichiometric, hexagonal crystal type films were prepared with substrate temperatures of 250°C and further annealed at 500°C. Cathodoluminescence, photoluminescence and electroluminescence properties are described and compared with radio frequency sputtered samples. (6 pages)Improving the efficiency of thin film electroluminescent displays
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950974
Alternating current thin film electroluminescent (ACTFEL) devices have been used in applications requiring small area emissive displays with both high resolution (300 pixels per inch), and high intensity (>3000 fL). These requirements have been met by increasing the luminescent efficiency of ACTFEL devices via two independent techniques: (1) Alternative device geometry for enhanced out coupling of light. (2) Materials engineering for enhanced generation of light. ACTFEL devices are essentially thin film capacitors across which an alternating field is applied. In the `on state', the capacitance of the phosphor layer collapses due to the internal transfer of charge from one interface to the other. Power dissipation in the `on state' is therefore dictated by the drive voltage, drive frequency and the `on state' capacitance. For all of the L-V measurements presented, the device area and drive frequency were held constant, so that at a particular voltage, the relative luminance values are equivalent to relative luminous efficiency values. Hence the efficiency of an ACTFEL device has been demonstrated to be improved by both the utilisation of reflected lateral emission, and by the inclusion of a barrier layer in tandem with high temperature annealing. (6 pages)Design and certification of a multiple concept system
http://dl-live.theiet.org/content/conferences/10.1049/cp_19940407
This paper describes an escape lighting system which uses a low energy electroluminescent lamp of a type which has been successfully used in the aircraft industry for a number of years. The theme of this paper is how the conceptual needs of an escape lighting system which is to be installed on offshore structures can be met. The design takes cognisance of the harsh environment which would exist on such a structure together with functional needs and the requirement for the system to operate in a potentially explosive atmosphere. It would also be necessary to cater for operation of the system during emergency shut down of the supplies on the structure. The overall description of this escape lighting system (known as Exitpath) is: EEx ia IIB [IIC] T4. This comprises: Lamps-EEx ia IIB T4; Power Supply-EEx em[ia] IIB T4; Battery Supply-EEx emd IIB T4, and during the paper some discussion is devoted to the reasons which led to the adoption of the various methods of explosion protection which have been employed.An analysis of the overall integrity of an escape route lighting system
http://dl-live.theiet.org/content/conferences/10.1049/cp_19940411
The author describes the testing and analysis of a low level escape route lighting system used in offshore platforms. It consists of electroluminescent strips enclosed in polycarbonate housing which is normally affixed to the wall some 25 cms above the the ground. The lights are powered by a 40 volt 1 kHz square wave derived from a battery backed up power source. The author discusses the analysis of the power supply and oscillators, batteries, electroluminescent strips, and the wiring.DC electroluminescence from PECVD grown thin films of silicon-rich silica
http://dl-live.theiet.org/content/journals/10.1049/el_19961122
The authors report the fabrication of an electroluminescent MOS device using microclustered silicon in silica as the active layer. A DC electroluminescence spectrum is shown and compared with photoluminescence from the same material. A current-voltage curve is presented which shows weak rectifying behaviour and is consistent with a space-charge limited structure with a high resistivity layer.See-through, multi-pixel organic emissive display
http://dl-live.theiet.org/content/journals/10.1049/el_19980623
A see-through multi-pixel emissive display has been demonstrated. The 8 × 12 pixel display, fabricated on a glass substrate, has two partially transparent electrodes that sandwich multi-layer, thin film organic materials. The fabrication approach is based on common integrated circuit processing techniques and can be extended to form active matrix addressed displays on silicon substrates.Pulsed KrF laser annealing of blue emitting SrS:Cu,Ag thin films
http://dl-live.theiet.org/content/journals/10.1049/el_20020878
The first successful attempt at utilising pulsed KrF (248 nm) laser annealing as a post-deposition process for RF sputtered SrS:Cu,Ag phosphor films used for thin film electroluminescent (TFEL) devices is presented. Using this novel annealing method, the luminance of the TFEL devices is observed to improve as laser fluence increases. Hence, the potential for luminance improvement of SrS:Cu,Ag TFEL devices without the need for a high temperature annealing process is demonstrated.Light emitting real-space transfer devices fabricated with strained GaAs/In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>As/AlGaAs heterostructures
http://dl-live.theiet.org/content/journals/10.1049/el_19960664
Light emitting devices based on real-space electron transfer are implemented with strained GaAs/InGaAs/AlGaAs heterostructures on GaAs substrates. Both GaAs channel and In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>As channel devices are fabricated. The device energy band diagrams are simulated by using the MEDICI program. The optical measurement shows that the photocurrent on/off ratio of InGaAs channel devices is better than that of GaAs channel devices.High-luminosity organic-dye-dispersed inorganic electroluminescent panel
http://dl-live.theiet.org/content/journals/10.1049/el_20072231
A novel high-luminosity organic-dye-dispersed inorganic electroluminescent (EL) panel is developed using a printing technique. An EL panel, having a Coumarin6-doped phosphor layer, was manufactured, which is expected to increase the efficiency of distributed-type inorganic EL panels. Therefore, a panel having a higher luminosity than conventional inorganic EL panels was obtained.Simultaneous three-state lasing in quantum dot laser at room temperature
http://dl-live.theiet.org/content/journals/10.1049/el.2010.1669
The first quantum dot laser under simultaneous three-state lasing operation at room temperature has been realised. The device exhibits ground state lasing at 1306 nm, the fist excited state lasing at 1213 nm and the second excited state lasing at 1152 nm synchronously. This is attributed to the long carrier relaxation time from higher energy levels to lower energy levels.Electrically driven ZnO nanoparticle light emitting device
http://dl-live.theiet.org/content/journals/10.1049/el_20081841
A light emitting device with commercially available ZnO nanoparticles as an active layer was realised without the help of organic support layers. A tight ZnO nanoparticle layer with thickness of 500 nm was spin coated on the top of an indium tin oxide fused silica substrate. After evaporation of a top aluminium electrode, diode-like <i xmlns="http://pub2web.metastore.ingenta.com/ns/">I</i>-<i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i> characteristics and a pronounced electroluminescence in the visible spectral range were obtained.Spontaneous emission control by 17 layers of three-dimensional photonic crystals
http://dl-live.theiet.org/content/journals/10.1049/el_20083634
17 stacked layers of three-dimensional photonic crystals containing light-emitters were constructed and the spontaneous emission characteristics investigated. Both an InGaAsP multiple quantum well light-emitting layer and artificial point defects were incorporated into the centre of the crystals. It is experimentally demonstrated that the spontaneous emission was suppressed by up to −30 dB and the artificial point defects yielded well-defined cavity modes with a minimum full-width-at-half-maximum of ∼4 nm.Photon emission in deep submicron Si <i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i>-MOSFET
http://dl-live.theiet.org/content/journals/10.1049/el_19971304
The photon emission phenomenon has been studied in deep submicron MOSFETs (down to 0.1 µm) in a wide drain and substrate voltage range. The authors show that the number of emitted photon is still large for low voltage operation. Moreover, using the influence of a substrate bias, it is shown that the photon emission phenomenon is unambiguously associated with the substrate current and cannot be correlated to the gate current.Micro-pixel arrays of bright organic electroluminescent devices for high definition displays
http://dl-live.theiet.org/content/journals/10.1049/el_19971396
Arrays of 600 micro-pixels of organic light emitting devices were fabricated by vacuum deposition of organic molecules. Pixels with dimensions as small as 20 × 20 µm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> were easily achieved. Individual pixels showed bright green light in excess of 28,500 cd/m<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> in CW mode.Laser processing for enhanced performance thin film electroluminescent devices
http://dl-live.theiet.org/content/journals/10.1049/el_20000568
A technique for enhancing the performance of thin film electroluminescent devices is presented. Thin film phosphors have been processed with 20 ns pulses of 880 mJ/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> laser irradiation from a 249 nm KrF excimer laser. Electroluminescent characterisation demonstrates a four-fold improvement in emitted luminous intensity, as compared to thermally annealed structures.1.52 µm electroluminescence from GaAs-based quantum dot bilayers
http://dl-live.theiet.org/content/journals/10.1049/el.2010.3203
InGaAs strain reducing layers (SRLs) are applied to InAs bilayer quantum dots (QDs) grown by molecular beam epitaxy on GaAs substrates. By control of the QD size and density and the composition of the SRLs, peak ground state electroluminescence of up to 1.52 µm is demonstrated from devices incorporating five QD bilayers, without the need for a metamorphic buffer layer.Emission enhancement of electrochemiluminescence device by mixing highly scattering medium
http://dl-live.theiet.org/content/journals/10.1049/el_20092246
Emission enhancement from an electrochemiluminescence (ECL) device of anthracene solution containing a mixture of highly scattering TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> nanoparticles was observed. It was confirmed experimentally that there exists an optimum quantity of the highly scattering TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub> nanoparticles assisting the emission enhancement in the ECL device of anthracene solution.Mid-infrared electroluminescence from device with changeable electron–hole distance
http://dl-live.theiet.org/content/journals/10.1049/el_20030045
A report is presented on the observation of mid-infrared electroluminescence from a multi-period bilayer type-II structure in which the effective interlayer separation is controlled by bias. The emission with powers in the microwatt range is characterised by a linear dependence of the photon energy on the bias.1.3 µm InAs/GaAs multilayer quantum-dot laser with extremely low room-temperature threshold current density
http://dl-live.theiet.org/content/journals/10.1049/el_20046692
A high growth temperature step used for the GaAs spacer layer is shown to significantly improve the performance of 1.3 µm multilayer InAs/GaAs quantum-dot lasers. Extremely low room-temperature continuous-wave threshold current densities of 32.5 and 17 A/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> are achieved for a three-layer device with as-cleaved facets and high-reflectivity coated facets, respectively.Red-emitting organic-dye-dispersed inorganic electroluminescent panel
http://dl-live.theiet.org/content/journals/10.1049/el_20082810
A red-emitting organic-dye-dispersed inorganic electroluminescent (EL) panel is developed using a printing technique. An EL device with Coumarin 6 and a 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran co-doped phosphor layer, which is expected to emit red light, was manufactured. Therefore, a red-emitting panel without a colour filter is obtained.Impulse response signature of a DCEL ZnS:Mn,Cu powder display determined by crosscorrelation
http://dl-live.theiet.org/content/journals/10.1049/ip-g-2.1991.0030
The voltage-luminous intensity transfer function for DC electroluminescence (DCEL) ZnS:Mn, Cu powder display panels has been determined by impulse response testing using crosscorrelation techniques. The investigation has revealed a signature characteristic featuring evidence of an internal feedback mechanism which is a function of the mean voltage causing luminescence. It has further shown that the time constant of the system is also a function of the mean voltage. Fourier transforms of the domain data indicate a second-order mechanism dominating the transfer function.Efficiency and response time of a DCEL ZnS : Mn Cu powder display determined by sinusoidal frequency analysis
http://dl-live.theiet.org/content/journals/10.1049/ip-g-2.1989.0032
The voltage-luminous intensity transfer function for DC electroluminescence (DCEL) ZnS: Mn, Cu powder display panels has been determined by the use of a small-amplitude sinusoidal drive-voltage biased on a DC voltage. Bode representation of this transfer function has revealed a lowpass bandwidth of 200 Hz. Evidence has shown that mean luminous intensity is strongly influenced by the harmonic content of the input voltage, which is limited by the 200 Hz system bandwidth. Consequently, the relationship between DCEL efficiency and system bandwidth has been investigated. The visual perception of luminous intensity has been included in the analysis to show that efficiency is also a function of the number of rows of pixels used in a particular DCEL display.Special issue paper. High-radiance long-lived l.e.d.s for analogue signalling
http://dl-live.theiet.org/content/journals/10.1049/piee.1976.0137
The design and evaluation of Burrus type GaAs-GaA1As double-heterojunction l.e.d.s suitable for application in analogue optical communication systems is described. Characteristics such as radiance, response time, linearity and reliability are considered. The coupling efficiencies of the l.e.d.s to optical fibres typical of those employed in practical systems are presented. Results are given of measurements made of device linearity as a function of drive level, active layer doping and ambient temperature. Implications of these linearity measurements on the use of the l.e.d.s for analogue signalling are discussed. Data on device linearity and reliability are presented, which show (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">a</i>, total harmonic distortion less than −50 dB (100 mA d.c., 100 mA peak to peak modulation at 5 MHz) and <i xmlns="http://pub2web.metastore.ingenta.com/ns/">b</i>, extrapolated halflives greater than 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sup> hours at 3 kA/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>.Cathodoluminescence of oxygen-implanted zinc-doped gallium phosphide
http://dl-live.theiet.org/content/journals/10.1049/el_19690153
Oxygen has been introduced by ion implantation into zinc-doped epitaxial gallium phosphide grown from the vapour phase. After annealing, cathodoluminescence from zinc-oxygen pairs is observed, having an efficiency approaching that of bulk zinc-oxygen doped solution-grown material. For a zinc concentration of 2 × 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">17</sup>cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−3</sup>, an optimum oxygen concentration for cathodoluminescence of 3 × 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">18</sup>cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−3</sup> is exhibited.GaP electroluminescent memory switch
http://dl-live.theiet.org/content/journals/10.1049/el_19730203
M.I.S. structures in which the semiconductor is GaP and the insulator a native oxide of GaP exhibit switchtng and non volatile memory properties as well as electroluminescence that is green under forward bias and orange under reverse bias. The switching and memory properties are thought to be due to a forming process in the oxide layer.Observation of recombination radiation in planar Gunn-effect devices
http://dl-live.theiet.org/content/journals/10.1049/el_19710128
Measurement of recombination radiation emitted from planar Gunn-effect devices having either plane parallel or concentric electrodes suggests that hole injection at the anode may be the most important mechanism for the thermal break down of these devices, as earlier proposed by Jeppsson and MarklundImproved technique for the preparation of Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>x</i></sub>Al<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1−<i>x</i></sub>As electroluminescent diodes
http://dl-live.theiet.org/content/journals/10.1049/el_19720012
An improved technique for the preparation of Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>x</i></sub>Al<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1−<i>x</i></sub>As electroluminescent diodes is described. Multilayer structures grown by liquid-phase epitaxy are used to achieve high external quantum efficiencies.<i xmlns="http://pub2web.metastore.ingenta.com/ns/">S</i> type current/voltage characteristics and recombination emission in Gunn diodes
http://dl-live.theiet.org/content/journals/10.1049/el_19700368
When impact ionisation occurs in Gunn diodes, recombination radiation must exist with photon energy less than the energy gap due to the Franz-Keldysh effect in the high-field domain. This radiation must be polarised along the field. The criterion for stimulated emission in the Gunn diode is derived. Stimulated emission takes place only outside the high-field domain and can be modulated with the frequency of the Gunn generation.Efficiency peaking in red-light-emitting gallium-phosphide diodes
http://dl-live.theiet.org/content/journals/10.1049/el_19690142
Measurements of the variation of efficiency with current of gallium-phosphide diodes emitting light at 690nm have shown a consistent relationship between the peak quantum efficiency and the current at which this peak occurs. This can be related to the number of zinc-oxygen pairs in nearest-neighbour states.Output saturation in GaP red lamps
http://dl-live.theiet.org/content/journals/10.1049/el_19690311
The variation of light output with current in a diode lamp is analysed. It is assumed that, while luminescent recombination processes saturate at high current, competing nonluminescent processes do not. The derived relationship is compared with published experimental work.New AC thin-film electroluminescent device with frequency-controlled brightness characteristics
http://dl-live.theiet.org/content/journals/10.1049/el_19860457
A novel thin-film electroluminescent device having a brightness/voltage characteristic depending strongly on the frequency of the excitation voltage is described. It is essentially a ZnS:Mn thin-film EL device of double-insulating-layer structure with a new dielectric layer of frequency-dependent impedance characteristic as the insulator.GaAs FET as a light transducer
http://dl-live.theiet.org/content/journals/10.1049/el_19850284
Conditions are described in which a power GaAs FET is sensitive to and emits light at the same time. With He-Ne 6328 Å light stimulation and white-light emission a transducer ratio of 0.005 was measured. Both the sensitivity to light and the light emission are very nonuniform across the device. Although each is a measure of device nonuniformity, no correlation between the two methods of nonuniformity measurement was observed.Blue electroluminescence from ZnSe/Langmuir-Blodgett film MIS diodes
http://dl-live.theiet.org/content/journals/10.1049/el_19870163
The electrical and electroluminescent properties of Au/phthalocyanine Langmuir-Blodgett film/ZnSe diodes are reported. Under forward bias, and at room temperature, the devices exhibited blue-white electroluminescence. Further investigation revealed two peaks in the spectrum: at 460nm and at 500nm. The 460nm peak coincides with the maximum output in the photoluminescence spectrum and is attributed to band-to-band recombination.White-light emission from GaAs m.o.s. structures
http://dl-live.theiet.org/content/journals/10.1049/el_19780316
Emission of light from GaAs m.o.s. structures with anodic native oxides is reported. The spectrum is continuous, covers the visible range and has substantial parts that have higher photon energies than the GaAs energy gap. A part of the emission therefore seems to originate from the amorphous native GaAs oxide with its wide energy gap of about 4.5 eV. The light appears white to the eye and its intensity, but not its spectral distribution, can be controlled by the bias applied to the m.o.s. structure.White-emitting a.c. electroluminescent powder layers for flat-panel television
http://dl-live.theiet.org/content/journals/10.1049/el_19760023
For application in future flat-panel television, where a thin-film transistor matrix on glass addresses a superimposed e.l. powder layer, we have developed e.l. layers which emit white light by using part of the blue e.l. emission to excite the fluorescence of organic dyes which are dissolved in the resinous embedding medium. Using a monograin particle layer and a black back electrode, we have achieved high visual contrast in a bright ambient, and operation at less than 50 V. Fabrication is described. The design can be extended to colour-t.v. panels.Bulk and junction effects in d.c. electroluminescent ZnS:Cu,Mn powder panels
http://dl-live.theiet.org/content/journals/10.1049/el_19800396
Current/voltage, current/brightness and capacitance values have been monitored as d.c. electroluminescent ZnS:Cu,Mn powder panels have been ‘formed’ to a series of voltages. Bulk effects are seen to be at least as important as junction effects to the generation of electroluminescence.Diffusion-induced disordering of Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.47</sub>In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.53</sub>As/InP multiple quantum wells with zinc
http://dl-live.theiet.org/content/journals/10.1049/el_19880619
Diffusing zinc into Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.47</sub>In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.53</sub>As/InP MQW layers is found to cause strong intermixing of the group III elements, which changes the composition in the quantum wells and barriers. As a result of this disordering the MQW bandgap is reduced in energy and the photoluminescence emission peak moves to longer wavelength.Electrofluorescent colloid light switch
http://dl-live.theiet.org/content/journals/10.1049/el_19800592
A low field electro-optic light switch mechanism is proposed, based on changes in the fluorescence from dye molecules absorbed to sepiolite clay particles. When tagged with acridine orange and suitably oriented in an electric field, sepiolite suspensions give fluorescence effects orders of magnitude greater than those for dye-tagged liquid crystals. Uses of the system are discussed.Conjugal lights
http://dl-live.theiet.org/content/journals/10.1049/ir_19960409
Polymers are generally excellent natural insulators, and electrically active polymers would appear to be a contradiction in terms. Here, the author reviews the progress of a company hoping to transform the flat-panel display business using these unlikely sounding materials.Silicon-carbide electroluminescent devices
http://dl-live.theiet.org/content/journals/10.1049/piee.1969.0060
Electroluminescent devices have been constructed from epitaxially grown <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i>-<i xmlns="http://pub2web.metastore.ingenta.com/ns/">n</i> junctions in silicon carbide. By suitable choice of material polytype and impurities, the luminescence can be controlled, to give various colours covering most of the visible spectrum. Brightnesses in excess of 100ft L (342cd/m<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>) at current densites of 10A/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>, have been achieved. The lamps operate at a few volts d.c. and 10–100mA, but pulsed operation at higher currents is possible, and the devices will respond to pulses with rise times below 1µS. Operating lives in excess of 15000h have been obtained at 50mA, with a constant light output. Arrays of lamps fabricated on a single crystal have been found suitable for applying information to photographic film, and as numerical displays. The luminescence intensity of these devices is, generally, proportional to input current, and the area of luminescence remains substantially constant. However, by adding a third electrode to the structure, it is possible to control the area of luminescence of the device with suitable biasing. These devices have applications as magnitude and tuning indicators.Electroluminescent panel devices
http://dl-live.theiet.org/content/journals/10.1049/ip-a-1.1980.0031
There are a number of different forms of electroluminescent panels which can be used for display purposes. The differences between these various constructions are described, and their properties and applications reviewed. Although almost all the electroluminescent devices which are in regular production are of the a.c., e.l. type; d.c., e.l. shows promise for certain types of small dynamic displays. In recent years the greatest advances have been in the technology of light emitting films (l.e.f.) and it is in this area of electroluminescence that the best prospects for future developments of a more sophisticated type of display device can be expected.Hot electron light emission from a GaInAsP/InP structure
http://dl-live.theiet.org/content/journals/10.1049/ip-opt_20010131
The GaInAsP/InP device described consists of an InP p-n junction with a GaInAsP quantum well placed on the n-side within the depletion region. Two ohmic contacts are diffused through the layers into the structure defining an active surface area. When a voltage is applied across these contacts in the plane of the layers, electrons on the n-side of the structure, and holes on the p-side are heated by the electric field. These carriers are captured by the quantum well and recombine, resulting in light emission from the surface. During operation the large built-in electric field remains. This affects the position of the subbands, and the overlap of the electron and hole wavefunctions via the quantum confined stark effect (QCSE), and is dependent on the position of the quantum well. The emission wavelength is modelled as a function of position of the GaInAsP quantum well within the built-in electric field of the InP p-n junction using self-consistent numerical one-dimensional solutions of the Poisson and Schrödinger equations. Two similar structures, differing only in the position of their quantum well are investigated experimentally.Fast modelling of the optical characteristics of electroluminescent pixel structures
http://dl-live.theiet.org/content/journals/10.1049/ip-opt_20010072
An analytic model of the optical behaviour of laterally light emitting thin film structures is developed. It is employed to calculate the outcoupled light of a pixel used in light emitting dot matrix displays such as laterally emitting thin film electroluminescent displays (LETFEL) with micromirrors. Consequently, one can identify the optimum pixel geometry. Here, the optical behaviour of the circular, square and hexagonal pixel geometry is modelled. The presented closed form solutions are based on a ray optics approximation whereby the absorption of the light within the light generating medium (phosphor material) and the transmission behaviour of the phosphor–air interface is taken into account, as well as the micromirror width. These solutions, however, neglect back reflected light. The effect of this neglect is investigated for square pixels by taking into account the first reflection. The model is applied to a typical LETFEL display with ZnS material doped with Mn. An optimal pixel diameter of 35 μm is estimated for that particular type of display.Large-area IR negative luminescent devices
http://dl-live.theiet.org/content/journals/10.1049/ip-opt_20030467
Negative luminescent (NL) devices, which to an IR observer appear colder than they actually are, have a wide range of possible applications, including for use as IR sources in gas-sensing systems and as thermal radiation shields in IR cameras. Additionally, these devices can be used as calibration sources for very large IR focal plane arrays and have many potential advantages over conventional calibration sources, including high-speed operation (for multi-point correction) and low power consumption. For many of these applications a large area ∼1cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> device which displays an, as large as possible, apparent temperature range is required. However, significant currents are required to reduce the carrier concentrations to the levels needed for maximum dynamic range. The authors have therefore used a novel micromachining technique to fabricate integrated optical concentrators in InSb/InAlSb and HgCdTe NL devices. Smaller area diodes can then be used to achieve the same absorption (e.g. for InSb an area reduction of 16 is possible) and the required currents are thus reduced. Recent results are presented from a large area ∼0.86<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> medium wavelength (MW) device incorporating integrated optical concentrators. The reverse saturation current of the device was measured to be ∼2.3 A/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>, which is significantly smaller than the value of ∼9 A/cm<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup> reported previously for similar devices without optical concentrators. In addition, the large apparent temperature drop of the device ∼20K for a detector of cut-off 6.5µm when under reverse bias, coupled with its large size, mean that this device would be appropriate for use as a calibration source for IR imagers.Bi-directional field effect light emitting and absorbing heterojunction with Ga<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.8</sub>In<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.2</sub>N<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.015</sub>As<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.985</sub> at 1250 nm
http://dl-live.theiet.org/content/journals/10.1049/ip-opt_20030051
The basic operation of a novel GaInNAs/GaAs based light emitting/absorbing device operating at 1250 nm is described. The device is a bi-directional field effect light emitting and absorbing heterojunction (BiFEEAH), which can simultaneously emit and detect light. This feature makes it possible to construct a wavelength converter, where one end of the device absorbs incoming light and the other end emits light at a different wavelength. The current device consists of a simple GaAs p–i–n structure, containing a single 90 Å GaInNAs quantum well in its intrinsic region. This is fabricated into a four contact device with separate n and p conducting channels.White-colour electroluminescence from porous-silicon diodes capped with organic conductive adduct
http://dl-live.theiet.org/content/journals/10.1049/ip-opt_20000566
Organic charge-transfer conductive adducts of tetrathiafulvalene (TTF) and bis (ethylenedithio) tetrathiafulvalene (ET) are proposed as materials for top electrical contacts in porous-silicon-based light-emitting devices. Semitransparent conductive adduct coatings were produced by impregnating PSi layers with a solution containing the desired adduct. Improvement in brightness (2.5×10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sup> fold) and luminous efficiency (10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">4</sup> fold) have been achieved. Devices made with top contacts of TTF(NO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>)<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.55</sub> and ET (NO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>)<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.67</sub> emit white light whereas those made with TTFI<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.71</sub> and TTF(SCN)<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.45</sub> emit yellow light. Internal luminous efficiency of 1.4l mW<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup> has been obtained for ET(NO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>)<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.67</sub>-capped devices. The carrier injection was found to obey a space-charge-limited current model.DC operated thin film electroluminescent device
http://dl-live.theiet.org/content/journals/10.1049/el_19950767
An improved version of a DC operated thin film electroluminescent device is proposed, which relies heavily on the nature of trapping states in a <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-</sup>-Si/ZnS:Mn heterodiode. Such a junction facilitates charge leakage from the inversion region of the silicon when films of ZnS are grown by sputtering in a sulphur-reduced environment. Alternatively, high resistivity films of ZnS are created by growth in a sulphur-enriched environment. Hence, the proposed structure is reverse biased <i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-</sup>-Si/ZnS(grown in Ar/O)/Y<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>/ZnS:Mn(grown in Ar/H<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>S) and has a transparent electrode. The thin film of Y<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> prevents diffusion of sulphur vacancies while facilitating electron tunnelling.Electroluminescent porous silicon device with an external quantum efficiency greater than 0.1% under CW operation
http://dl-live.theiet.org/content/journals/10.1049/el_19950831
The authors report an all solid state, VLSI compatible, electroluminescent device based on porous silicon with an external quantum efficiency greater than 0.1% under CW operation. The emission, which is broadband and peaks at 600 nm, is detected above a low threshold current density and voltage of 0.01 Am<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">-2</sup> and 2.3 V, respectively.TFEL optoelectronic integrated circuit on Si
http://dl-live.theiet.org/content/journals/10.1049/el_19940890
A unique optoelectronic integrated circuit fabricated with AC thin film electroluminescent (TFEL) devices directly onto the drain of an Si DMOS transistor is demonstrated. DMOS switching controls the high voltage ratio between the TFEL device and DMOS transistor. Active matrix addressing for electroluminescent devices is demonstrated using CMOS circuitry.