While Quantum Dots (QDs) have found commercial success in display applications, there are currently no widely available solid state lighting products making use of QD nanotechnology. In order to have real-world success in today’s lighting market, QDs must be capable of being placed in on-chip configurations, as remote phosphor configurations are typically much more expensive. Here we demonstrate solid-state lighting devices made with on-chip QDs. These devices show robust reliability under both dry and wet high stress conditions. High color quality lighting metrics can easily be achieved using these narrow, tunable QD downconverters: CRI values of Ra > 90 as well as R9 values > 80 are readily available when combining QDs with green phosphors. Furthermore, we show that QDs afford a 15% increase in overall efficiency compared to traditional phosphor downconverted SSL devices. The fundamental limit of QD linewidth is examined through single particle QD emission studies. Using standard Cd-based QD synthesis, it is found that single particle linewidths of 20 nm FWHM represent a lower limit to the narrowness of QD emission in the near term.

Majority of w-LEDs (white light emitting diodes) are based on InGaN blue-LED associated with phosphors exhibiting complementary color emissions to generate required white light output. However, such complementary color mixing with the lack of violet and mainly orange-red color results in poor color-rendering index (CRI). To achieve better resolution of natural white color, recent trends on w-LEDs are focused on broadband visible emitting phosphors excitable with near UV or violet LEDs. Here, we present novel amorphous yttrium-aluminum-borate (g-YAB) phosphors exhibiting broad visible emission under UV-violet excitations. These g-YAB phosphors show high internal quantum yields (~90 %) under 365 nm excitation, possess good thermal stability over 200°C and maintains the performance for continuous and repeated operations that are ideal for the development of near UV-violet excitable w-LEDs with high color rendering ability.

Graphene has been touted as an ideal material for GaN LED transparent conductive layers due its high optical transparency and high electron mobility. However, many issues exist with graphene-LED integration. These include contamination from metal catalysts and manual transfer; graphene material non-uniformities over large (wafer-scale) areas; incompatibility with LED device processing; and high manufacturing costs for large-areas of material. In this work, we demonstrate graphene as a transparent contact layer for GaN LEDs which solves all of these issues. Our results prove zero contamination, with excellent material uniformity and full LED processing compatibility. Thus, we have for the first time shown a graphene fabrication process suitable for industrial GaN LED integration.

In MOCVD growth, two key factors for growing a p-type structure, when the modulation growth or delta-doping technique is used, include Mg memory and diffusion. With high-temperature growth (>900 degree C), doped Mg can diffuse into the under-layer. Also, due to the high-pressure growth and growth chamber coating in MOCVD, plenty Mg atoms exist in the growth chamber for a duration after Mg supply is ended. In this situation, Mg doping continues in the following designated un-doped layers. In this paper, we demonstrate the study results of Mg preflow, memory, and diffusion. The results show that pre-flow of Mg into the growth chamber can lead to a significantly higher Mg doping concentration in growing a p-GaN layer. In other words, a duration for Mg buildup is required for high Mg incorporation. Based on SIMS study, we find that with the pre-flow growth, a high- and a low-doping p-GaN layer are formed. The doping concentration difference between the two layers is about 10 times. The thickness of the high- (low-) doping layer is about 40 (65) nm. The growth of the high-doping layer starts 10-15 min after Mg supply starts (Mg buildup time). The diffusion length of Mg into the AlGaN layer beneath (Mg content reduced to <5%) is about 10 nm. The memory time of Mg in the growth chamber is about 60 min, after which the Mg doping concentration is reduced to <1%.

This paper demonstrates that when InGaN LEDs are submitted to a constant reverse bias, they can show a time-dependent breakdown, that leads to the catastrophic failure of the devices. By submitting green and blue LEDs to constant voltage stress in the range between -40 V and -60 V we demonstrate that: (i) under reverse bias conditions, current is focused on localized paths, whose positions can be identified by electroluminescence measurements, and that originate from the presence of extended defects; (ii) during a constant voltage stress, the reverse current of the LEDs gradually increases; (iii) for longer stress times, all devices show a time-dependent breakdown; (iv) time-to-failure has an exponential dependence on stress voltage, and is Weibull-distributed.

We report the mass production of blue LEDs on dry-etched patterned sapphire substrates using the AIX R6 tool in a 31×4" configuration. The system was operated in a continuous run mode, i.e. cleaning the showerhead after a series of LED runs. Production stability was characterized by monitoring of wavelength, light output power (LOP), and electrostatic discharge (ESD) yields. We developed a dynamic multi-zone Topside Temperature Control and the TEQualizer function. The TEQualizer function is based on a 400nm pyrometry open loop wafer surface temperature control, using Inside P400 by Laytec. Combining this wafer-to-wafer and run -to-run temperature stability improvement with an optimized wafer carrier, we demonstrated an on-wafer uniformity of stdv of 1.1nm, a wafer-to-wafer uniformity of stdv 1.1nm and a run-to-run reproducibility of stdv <1nm, resulting in a total wafer area wavelength yield of >90% in a 6 nm bin. LOP stability was demonstrated within a 3% window with no visible run-to-run trend. An absolute buffer layer growth temperature window was defined through a Design of Experiment on buffer layers targeting best ESD yield - in particular looking into defect related morphology and its correlation with Inside P400 readings. We have demonstrated an ESD yield >90% in continuous run mode to be used in the mass production of InGaN based blue LEDs.

GaN-based nanowire arrays have been grown on (001)Si substrate by plasma-assisted molecular beam epitaxy and their structural and optical properties have been determined. In_xGa_1-xN disks inserted in the nanowires behave as quantum dots with emission ranging from visible to near-infrared. We have exploited these nanowire heterostructure arrays to realize light-emitting diodes and diode lasers in which the quantum dots form the active light emitting media. The fabrication and characteristics of 630nm light-emitting diodes and 1.3μm edge-emitting diode lasers are described.

We present classical and quantum light generation based on various types of group III-nitride micro- and nano-structures. We fabricated three-dimensional GaN-based pyramidal, annular, columnar, and tapered rod structures, on which InGaN/GaN quantum wells structures were grown by metal-organic chemical vapor deposition. We demonstrate phosphor-free white-color light emission with pyramidal and annular structures, unidirectional light propagation in energy-gradient, tapered core-shell rod structures, ultrafast single photon generation from a quantum dot formed at the apex of pyramid structures, and exciton-polariton formation at room-temperature in bulk GaN and GaN/InGaN core-shell rod structures.

Light emitting diodes (LEDs) are used to very diverse fields because of their high efficiency and long life time. Especially, GaN-based LEDs has good properties such as high power and electrical stability, so it can be used for light source in many devices. However, because of large difference of refractive index between SiC substrate of LEDs and air, Fresnel reflection loss and Total internal reflection loss are occurred. For that reason, light extraction efficiency of LEDs is very low. In this study, we fabricate Alumina based scattering film and show light extraction efficiency of LEDs can be enhanced through attaching scattering film on SiC substrate. Alumina nanowires were fabricated by wet etching process of porous alumina layer. Nanowires were collapsed randomly by capillary force of water during drying process forming microscale ridges. This scattering film has extremely high transmittance and scattering value which is determined by etching time. The effective refractive index of the film lies between the refractive index of SiC and air. So attached scattering film on SiC substrate of LEDs creates gradually varying index distribution reducing Fresnel reflection loss. Microscale ridges of scattering film play as light scatterers, and incidence light scattered in all direction reducing incident angle dependence so they can reduce total internal reflection loss. Light extraction efficiency of scattering film attached LED is about 20% higher than bare LED.

Cascaded InAs/GaSb superlattice light emitting diodes are being developed for broadband, high radiance light sources for spectroscopy, and advanced technologies using large format arrays. Cascading is shown to allow broadening of the SLED spectral output, tuning of the electrical characteristics, and boosting of the maximum output power and efficiency. Wallplug efficiencies are found to be low, but internal quantum efficiency very high. It is anticipated that external quantum efficiency can be significantly increased by using strategies to help extract the light from these high index materials.

Besides lighting, LEDs can be used for indoor data transmission. Therefore, a large modulation bandwidth becomes an important target in the development of visible LED. In this regard, enhancing the radiative recombination rate of carriers in the quantum wells of an LED is a useful method since the modulation bandwidth of an LED is related to the carrier decay rate besides the device RC time constant To increase the carrier decay rate in an LED without sacrificing its output power, the technique of surface plasmon (SP) coupling in an LED is useful. In this paper, the increases of modulation bandwidth by reducing mesa size, decreasing active layer thickness, and inducing SP coupling in blue- and green-emitting LEDs are illustrated. The results are demonstrated by comparing three different LED surface structures, including bare p-type surface, GaZnO current spreading layer, and Ag nanoparticles (NPs) for inducing SP coupling. In a single-quantum-well, blue-emitting LED with a circular mesa of 10 microns in radius, SP coupling results in a modulation bandwidth of 528.8 MHz, which is believed to be the record-high level. A smaller RC time constant can lead to a higher modulation bandwidth. However, when the RC time constant is smaller than ~0.2 ns, its effect on modulation bandwidth saturates. The dependencies of modulation bandwidth on injected current density and carrier decay time confirm that the modulation bandwidth is essentially inversely proportional to a time constant, which is inversely proportional to the square-root of carrier decay rate and injected current density.

A novel design for high brightness planar technology light-emitting diodes (LEDs) and LED on-wafer arrays on absorbing substrates is proposed. The design integrates features of passive dielectric cavity deposited on top of an oxide– semiconductor distributed Bragg reflector (DBR), the p–n junction with a light emitting region is introduced into the top semiconductor λ/4 DBR period. A multilayer dielectric structure containing a cavity layer and dielectric DBRs is further processed by etching into a micrometer–scale pattern. An oxide–confined aperture is further amended for current and light confinement. We study the impact of the placement of the active region into the maximum or minimum of the optical field intensity and study an impact of the active region positioning on light extraction efficiency. We also study an etching profile composed of symmetric rings in the etched passive cavity over the light emitting area. The bottom semiconductor is an AlGaAs–AlAs multilayer DBR selectively oxidized with the conversion of the AlAs layers into AlO_x to increase the stopband width preventing the light from entering the semiconductor substrate. The approach allows to achieve very high light extraction efficiency in a narrow vertical angle keeping the reasonable thermal and current conductivity properties. As an example, a micro-LED structure has been modeled with AlGaAs-AlAs or AlGaAs-AlO_x DBRs and an active region based on InGaAlP quantum well(s) emitting in the orange spectral range at ~610 nm. A passive dielectric SiO₂ cavity is confined by dielectric Ta₂O₅/SiO₂ and AlGaAs-AlO_x DBRs. Cylindrically–symmetric structures with multiple ring patterns are modeled. It is demonstrated that the extraction coefficient of light to the air can be increased from 1.3% up to above 90% in a narrow vertical angle (full width at half maximum (FWHM) below 20°). For very small oxide–confined apertures ~100nm the narrowing of the FWHM for light extraction can be reduced down to 5°. Consequently high efficiency high brightness arrays of micro-LEDs becomes possible. For single emitters the approach is particularly interesting for oscillator strength engineering allowing high speed data transmission and for single photonics applying single quantum dot (QD) emitters and allowing >90% coupling of the emission into single mode fiber. We also note that for longer wavelength (~1300nm) QDs the thickness of the layers and surface patterns significantly increase allowing greatly reduced processing tolerances and applying further simplifications due to the possibility of using high contrast GaAs-AlO_x DBRs.

UV-LEDs are of great interest for applications like disinfection, gas sensing, and phototherapy. The cost sensitive LEDs are commonly grown by MOVPE on transparent AlN/sapphire templates. The large thermal and lattice mismatch between AlN and sapphire generates a very high dislocation density (DD) and causes big challenges in strain management. The threading dislocation density should be reduced to the order of low 108cm-2 for high internal efficiency of the AlGaN based UV-LED structures. The TDD will be reduced mainly by dislocation annihilation during the growth of thick Al(Ga)N layers, which is a challenge in terms of strain management. We present how in-situ reflectometry and curvature measurement (EpiCurveTT(at)LayTec) in commercial multiwafer growth reactors helps to optimize the growth processes concerning growth rates, surface roughening and avoidance of layer cracking on 2inch substrates and enhance the reproducibility of epitaxial growth. The growth of up to 3 μm thick planar AlN templates and up-to 10 μm thick AlN/sapphire templates by epitaxial lateral overgrowth of stripe patterned templates for UV-C LED structures will be highlighted. The implementation of different types of AlN/GaN superlattices for the subsequent growth of up to 5μm thick Al0.5Ga0.5N layer for UVB LED structures will be shown. Correlations to ex-situ measurements like X-ray diffraction and TEM analysis of defects in the LED structures will be shown. Some challenges of in-situ control through very narrow viewports as in Close Coupled Showerhead reactors will be discussed as well as the influence of silicon doping on curvature and dislocation density in Al(Ga)N layers.

The surface plasmon (SP) resonance was used to increase the emission efficiencies toward high efficiency light-emitting diodes (LEDs). We obtained the enhancements of the electroluminescence from the fabricated plasmonic LED device structure by employing the very thin p⁺-GaN layer. The further enhancements should be achievable by optimization of the metal and device structures. Next important challenge is to extend this method from the visible to the deep UV region. By using Aluminum, we obtained the enhancements of emissions at ~260 nm from AlGaN/AlN quantum wells. We succeeded to control the SP resonance by using the various metal nanostructures. These localized SP resonance spectra in the deep-UV regions presented here would be useful to enhance deep UV emissions of super wide bandgap materials such as AlGaN/AlN. We believe that our approaches based on ultra-deep UV plasmonics would bring high efficiency ultra-deep UV light sources.

High power LEDs have conquered the mass market in recent years. Besides the main development focus to achieve higher productivity in the field of visible semiconductor LED processing, the wavelength range is further enhanced by active research and development in the direction of UVA / UVB / UVC. UVB and UVC LEDs are new and promising due to their numerous advantages. UV LEDs emit in a near range of one single emission peak with a width (FWHM) below 15 nm compared to conventional mercury discharge lamps and xenon sources, which show broad spectrums with many emission peaks over a wide range of wavelengths. Furthermore, the UV LED size is in the range of a few hundred microns and offers a high potential of significant system miniaturization. Of course, LED efficiency, lifetime and output power have to be increased [1]. Lifetime limiting issues of UVB/UVC-LED are the very high thermal stress in the chip resulting from the higher forward voltages (6-10 V @ 350 mA), the lower external quantum efficiency, below 10 % (most of the power disappears as heat), and the thermal resistance Rth of conventional LED packages being not able to dissipate these large amounts of heat for spreading. Beside the circuit boards and submounts which should have maximum thermal conductivity, the dimension of contacts as well as the interconnection of UV LED to the submount/package determinates the resolvable amount of heat [2]. In the paper different innovative interconnection techniques for UVC-LED systems will be discussed focused on the optimization of thermal conductivity in consideration of the assembly costs. Results on thermal simulation for the optimal contact dimensions and interconnections will be given. In addition, these theoretical results will be compared with results on electrical characterization as well as IR investigations on real UV LED packages in order to give recommendations for optimal UV LED assembly.

The paper reports the analysis of (In)AlGaN-based UV-B LEDs degradation under constant current stress, and investigates the impact of defects in changing the devices electro-optical performance. The study is based on combined electro-optical characterization, deep-level transient- (DLTS) and photocurrent spectroscopy. UV-B LEDs show a decrease of the optical power during stress, more pronounced at low measuring current levels, indicating that the degradation is related to an increase of Shockley-Read-Hall (SRH) recombination. DLTS measurements allowed the identification of three defects, in particular one ascribed to Mg-related acceptor traps presence. Photocurrent spectroscopy allows the localization of the defects close to the mid-gap.

Ultraviolet light-emitting diode (UV LED) adoption is accelerating; they are being used in new applications such as UV curing, germicidal irradiation, nondestructive testing, and forensic analysis. In many of these applications, it is critically important to produce a uniform light distribution and consistent surface irradiance. Flat panes of fused quartz, silica, or glass are commonly used to cover and protect UV LED arrays. However, they don’t offer the advantages of an optical lens design. An investigation was conducted to determine the effect of a secondary glass optic on the uniformity of the light distribution and irradiance. Glass optics capable of transmitting UV-A, UV-B, and UV-C wavelengths can improve light distribution, uniformity, and intensity. In this work, two simulation studies were created to illustrate distinct irradiance patterns desirable for potential real world applications. The first study investigates the use of a multi-UV LED array and optic to create a uniform irradiance pattern on the flat two dimensional (2D) target surface. The uniformity was improved by designing both the LED array and molded optic to produce a homogenous pattern. The second study investigated the use of an LED light source and molded optic to improve the light uniformity on the inside of a canister. The case study illustrates the requirements for careful selection of LED based on light distribution and subsequent design of optics. The optic utilizes total internal reflection to create optimized light distribution. The combination of the LED and molded optic showed significant improvement in uniformity on the inner surface of the canister. The simulations illustrate how the application of optics can significantly improve UV light distribution which can be critical in applications such as UV curing and sterilization.

Efficiency droop and the green gap are challenges to InGaN/GaN light emitting diodes (LEDs). Defects have been suggested to contribute to both effects, so understanding the origin of defects and their impact on LED performance is important to improving efficiency. This talk describes the use of deep level optical spectroscopy (DLOS) to characterize deep level defects in quantum well (QW) and quantum barrier (QB) regions of InGaN LEDs. The spatial dependence of deep level defect density in the MQW region and the evolution of QW deep level defects with indium alloying will be discussed.

We investigate the luminescence distribution in the multi quantum well (MQW) region of polar III-nitride light emitting diodes (LED) operating in the blue spectral range by means of carrier transport simulations. The MQW region is modeled with an equivalent circuit. It is demonstrated that the MQW barriers primarily affect the hole transport. The electron scattering from continuum to bound quantum well states has a major impact on the electron transport. A nearly uniform luminescence distribution in the MQW region is achieved through a re-distribution of the luminescence from the n-side to the p-side QW with increasing current. We show that the re-distribution is seen through a decrease of the ideality factor in the MQW region and promoted by the asymmetry of the electron and hole transport.

High-power operation of conventional GaN-based light-emitting diodes (LEDs) is severely limited by current crowding, which increases the bias voltage of the LED, concentrates light emission close to the p-type contact edge, and aggravates the efficiency droop. Fabricating LEDs on thick n-GaN substrates alleviates current crowding but requires the use of expensive bulk GaN substrates and fairly large n-contacts, which take away a large part of the active region (AR). In this work, we demonstrate through comparative simulations how the recently introduced diffusion-driven charge transport (DDCT) concept can be used to realize lateral heterojunction (LHJ) structures, which eliminate most of the lateral current crowding. Specifically in this work, we analyze how using a single-side graded AR can both facilitate electron and hole diffusion in DDCT and increase the effective AR thickness. Our simulations show that the increased effective AR thickness allows a substantial reduction in the efficiency droop at large currents, and that unlike conventional 2D LEDs, the LHJ structure shows practically no added efficiency loss or differential resistance due to current crowding. Furthermore, as both electrons and holes enter the AR from the same side without any notable potential barriers in the LHJ structure, the LHJ structure shows an additional wall-plug efficiency gain over the conventional structures under comparison. This injection from the same side is expected to be even more interesting in multiple quantum well structures, where carriers typically need to surpass several potential barriers in conventional LEDs before recombining. In addition to simulations, we also demonstrate selective-area growth of a finger structure suitable for operation as an LHJ device with 2µm distance between n- and p-GaN regions.

Improvement of thermal stability of green quantum dot light emitting diodes (QD-LEDs) was demonstrated by using composition-gradient thick-shell CdSe@ZnS/ZnS quantum dots (QDs). The electroluminescence intensity only decreased 3% even when the operation temperature was elevated to 110 °C. The current efficiency roll-off effect was improved nearly 200% under higher current density. Thick-shell QDs with low defective structure could effectively prevent the electron-hole pairs from nonradiative Auger recombination and avoid the thermal-stress-induced expansion at higher temperatures and driving current. The maximum current efficiency of the thick-shell-device is 10.3 cd/A, which is much higher than 1.57 cd/A for the conventional thin-shell-device.

The wall-plug efficiency of modern light-emitting diodes (LEDs) has far surpassed all other forms of lighting and is expected to improve further as the lifetime cost of a luminaire is today dominated by the cost of energy. The drive towards higher efficiency inevitably opens the question about the limits of future enhancement. Here, we investigate thermoelectric pumping as a means for improving efficiency in wide-bandgap GaN based LEDs. A forward biased diode can work as a heat pump, which pumps lattice heat into the electrons injected into the active region via the Peltier effect. We experimentally demonstrate a thermally enhanced 450 nm GaN LED, in which nearly fourfold light output power is achieved at 615 K (compared to 295 K room temperature operation), with virtually no reduction in the wall-plug efficiency at bias V < ℏω/q. This result suggests the possibility of removing bulky heat sinks in high power LED products. A review of recent high-efficiency GaN LEDs suggests that Peltier thermal pumping plays a more important role in a wide range of modern LED structures that previously thought – opening a path to even higher efficiencies and lower lifetime costs for future lighting.

As solid-state lighting adoption moves from bulb socket replacement to lighting system engineering, luminaire manufacturers are beginning to actualize far greater cost savings through luminaire optimization rather than the simplistic process of component cost pareto management. Indeed, there are an increasing number of applications in which we see major shifts in the value chain in terms of increasing the L1 (LED) and L2 (LED array on PCB) value. The L1 value increase stems from a number of factors ranging from simply higher performing LEDs reducing the LED count, to L1 innovation such as high voltage LEDs, optimizing driver efficiency or to the use of high luminance LEDs enabling compact optics, allowing not only more design freedom but also cost reduction through space and weight savings. The L2 value increase is realized predominantly through increasing L2 performance with the use of algorithms that optimize L1 selection and placement and/or through L2 integration of drivers, control electronics, sensors, secondary lens and/or environmental protection, which is also initiating level collapse in the value chain. In this paper we will present the L1 and L2 innovations that are enabling this disruption as well as provide examples of fixture/luminaire level benefits.

Inorganic light emitting diodes (LEDs) serve as bright pixel-level emitters in displays, from indoor/outdoor video walls with pixel sizes ranging from one to thirty millimeters to micro displays with more than one thousand pixels per inch. Pixel sizes that fall between those ranges, roughly 50 to 500 microns, are some of the most commercially significant ones, including flat panel displays used in smart phones, tablets, and televisions. Flat panel displays that use inorganic LEDs as pixel level emitters (μILED displays) can offer levels of brightness, transparency, and functionality that are difficult to achieve with other flat panel technologies. Cost-effective production of μILED displays requires techniques for precisely arranging sparse arrays of extremely miniaturized devices on a panel substrate, such as transfer printing with an elastomer stamp. Here we present lab-scale demonstrations of transfer printed μILED displays and the processes used to make them. Demonstrations include passive matrix μILED displays that use conventional off-the shelf drive ASICs and active matrix μILED displays that use miniaturized pixel-level control circuits from CMOS wafers. We present a discussion of key considerations in the design and fabrication of highly miniaturized emitters for μILED displays.

LUMENTILE (LUMinous ElectroNic TILE) is a project funded by the European Commission with the goal of developing a luminous tile with novel functionalities, capable of changing its color and interact with the user. Applications include interior/exterior tile for walls and floors covering, high-efficiency luminaries, and advertising under the form of giant video screens. High overall electrical efficiency of the tile is mandatory, as several millions of square meters are foreseen to be installed each year. Demand is for high uniformity of the illumination of the top tile surface, and for high optical extraction efficiency. These features are achieved by smart light management, using a new approach based on light guiding slab and spatially selective light extraction obtained using both diffusion and/or reflection from the top and bottom interfaces of the optical layer. Planar and edge configurations for the RGB LEDs are considered and compared. A square shape with side length from 20cm to 60cm is considered for the tiles. The electronic circuit layout must optimize the electrical efficiency, and be compatible with low-cost roll-to-roll production on flexible substrates. LED heat management is tackled by using dedicated solutions that allow operation in thermally harsh environment. An approach based on OLEDs has also been considered, still needing improvement on emitted power and ruggedness.

Three-dimensional (3D) photonic crystals have potential in solid state lighting applications due to their advantages over conventional planar thin film devices. Periodicity in a photonic crystal structure enables engineering of the density of states to improve spontaneous light emission according to Fermi’s golden rule. Unlike planar thin films, which suffer significantly from total internal reflection, a 3D architectured structure is distributed in space with many non-flat interfaces, which facilitates a substantial enhancement in light extraction. We demonstrate the fabrication of 3D nano-architectures with octahedron geometry that utilize luminescing silicon nanocrystals as active media with an aluminum cathode and indium tin oxide anode towards the realization of a 3D light emitting device. The developed fabrication procedure allows charge to pass through the nanolattice between two contacts for electroluminescence. These initial fabrication efforts suggest that 3D nano-architected devices are realizable and can reach greater efficiencies than planar devices.

The problems of dressability the solid minerals are attracted attention of specialists, where the extraction of mineral raw materials is a significant sector of the economy. There are a significant amount of mineral ore dressability methods. At the moment the radiometric dressability methods are considered the most promising. One of radiometric methods is method photoluminescence. This method is based on the spectral analysis, amplitude and kinetic parameters luminescence of minerals (under UV radiation), as well as color parameters of radiation. The absence of developed scientific and methodological approaches of analysis irradiation area to UV radiation as well as absence the relevant radiation sources are the factors which hinder development and use of photoluminescence method. The present work is devoted to the development of multi-element UV radiation source designed for the solution problem of analysis and sorting minerals by their selective luminescence. This article is presented a method of theoretical modeling of the radiation devices based on UV LEDs. The models consider such factors as spectral component, the spatial and energy parameters of the LEDs. Also, this article is presented the results of experimental studies of the some samples minerals.

The description of the LED optical-electronic lighting system of plants for stimulation of growth and maturing of fruits of different cultures is provided in this work. Also the results of experimental research on the selection of components are presented. The results of energy calculations and 3D modeling of the distribution of the radiation fluxes generated from the source are included. Moreover, the design of optoelectronic plant lighting system layout was proposed.

We report on the measurements of aerosol and cloud vertical structure in New York City (NYC) using the first polarization Micro pulse Lidar (MPL) located at the City University of New York (CUNY). MPL operation, setup, data collection and correction will be introduced. Preliminary results and comparison analysis between 2015 and 2016 of cloud vertical structure and the Planetary Boundary Layer (PBL) above NYC will be discussed. An investigation analysis of the impact of NYC rush hour pollution on the level of PBL depth will be introduced using the MPL measurements (such as temporal and spatial trends in aerosol and cloud structure). Applications of the MPL tow-polarization channels will be investigated. Potential future studies and collaborations in protecting NYC against environmental disasters by employing more devices along with MPL real-time data will be emphasized. For pedagogical purposes, a lab module was developed to be implemented in the newly developed undergraduate track in Earth System Science and Environmental Engineering (ESE) at LaGuardia Community College of CUNY (LaGCC), more details will be presented.

To study the feasibility and quality of recycled glass phosphor waste for LED packaging, the experiments were conducted to compare optical characteristics between fresh color conversion layer and that made of recycled waste. The fresh color conversion layer was fabricated through sintering pristine mixture of Y.A.G. powder [yellow phosphor (Y₃AlO₁₂ : Ce³⁺). Those recycled waste glass phosphor re-melted to form Secondary Molten Glass Phosphor (S.M.G.P.). The experiments on such low melting temperature glass results showed that transmission rates of S.M.G.P. are 9% higher than those of first-sintered glass phosphor, corresponding to 1.25% greater average bubble size and 36% more bubble coverage area in S.M.G.P. In the recent years, high power LED modules and laser projectors have been requiring higher thermal stability by using glass phosphor materials for light mixing. Nevertheless, phosphor and related materials are too expensive to expand their markets. It seems a right trend and research goal that recycling such waste of high thermal stability and quality materials could be preferably one of feasible cost-down solutions. This technical approach could bring out brighter future for solid lighting and light source module industries.

InAs/GaSb superlattice light-emitting diodes are a promising technology for progressing the state-of-the art infrared scene projectors. By targeting a specific band of interest, they are able to achieve apparent temperatures greater than that of conventional resistor arrays and settling times on the order of nanoseconds. We report the fabrication of a dual-color infrared InAs/GaSb superlattice light-emitting diode array for operation in the mid-wave infrared. By stacking two superlattice structures back-to-back with a conductive layer separating them, independently operable, dual-color, cascaded InAs/GaSb superlattice light-emitting diodes were grown via molecular beam epitaxy on (100) GaSb substrates. At 77K, the emitted wavelengths are in the 3.2-4.2μm and 4.2-5.2μm range, with peak wavelengths at 3.81μm and 4.72μm. Using photolithography and wet etching, a 512×512 array of 48μm-pitch pixels were fabricated and hybridized to a silicon read-in integrated circuit. Test arrays with an 8×8 matrix of pixels demonstrated greater than 2 W/cm²˙sr for the 4.7μm emitter and greater than 5W/cm²˙sr for the 3.8μm emitter; the lower radiance in the long-wave emitter is due to a small active region volume left after fabrication. These respectively correspond to apparent temperatures greater than 1400K and 2000K in the 3-5μm band including fill factor.

The overall performance of the Light-emitting diode, LED package is critically affected by the heat attribution. In this study, open source software - Elmer FEM has been utilized to study the thermal analysis of the LED package. In order to perform a complete simulation study, both Salome software and ParaView software were introduced as Pre and Postprocessor. The thermal effect of the LED package was evaluated by this software. The result has been validated with commercially licensed software based on previous work. The percentage difference from both simulation results is less than 5% which is tolerable and comparable.

The demand for the high Lumens output on the commercialized Light-emitting diode, LED bulb has resulted in the increase of operating power and generation of heat. A study on the thermal performance of commercialized LED bulbs was done by using Elmer finite element simulation method. The variation approach was limited to input power (2 Watt- 10 Watt) and the heat performance was compared. The result gives a comparison of the variation of the model and the heat distribution. Analysis showed that the input power and bulb geometry give direct effect on the junction temperature.