Vertical Light-emitting Diodes Research Articles

Enhancing lavender (Lavandula angustifolia Mill.) propagation in vertical farming system: Investigating the impact of LED red-to-blue ratios and subsequent post-potting growth dynamics

This study aims to examine the influence of red-to-blue (R:B) LED light ratios on the propagation of Lavandula angustifolia within a vertical farming system. Additionally, it seeks to evaluate the persistent effects of LED lighting treatments on post-potting development in a glasshouse.The objective of this study is to assess how different R:B LED light ratios impact Lavandula angustifolia propagation in a vertical farming system and to analyze the enduring effects of these lighting treatments during the post-potting development stage in a glasshouse.The study consists of two phases. In the initial phase, an analysis was conducted on root emergence, root and shoot biomass, chlorophyll content, and flower bud emergence. Two LED treatments, labeled L1 and L2, were employed, with specific R:B ratios (7:1 and 9:1) and light intensities set at 140 µmol m−2 s−1 and 100 µmol m−2 s−1, respectively. Correlation and regression analyses were performed to understand the relationships among the various parameters.In Phase One, the L1 and L2 LED treatments significantly enhanced root emergence and biomass. Notably, the R:B ratios of 7:1 and 9:1, with corresponding intensities of 140 µmol m−2 s−1 and 100 µmol m−2 s−1, demonstrated substantial improvements. In the subsequent glasshouse phase, plants previously treated with L1 exhibited superior plant height and shoot biomass.The findings of this study highlight the intricate relationships among different parameters, providing valuable insights for lavender cultivation practices. The positive outcomes, particularly observed in the L1 treatment, emphasize the potential of vertical farming systems and LED lighting in optimizing lavender growth dynamics. This study underscores the importance of specific R:B ratios, contributing to sustainable propagation strategies, and acknowledges the space-efficient nature of vertical farming systems.

Electroluminescent vertical tunneling junctions based on WSe2 monolayer quantum emitter arrays: Exploring tunability with electric and magnetic fields

We experimentally demonstrate the creation of defects in monolayer WSe2 via nanopillar imprinting and helium ion irradiation. Based on the first method, we realize atomically thin vertical tunneling light-emitting diodes based on WSe2 monolayers hosting quantum emitters at deterministically specified locations. We characterize these emitters by investigating the evolution of their emission spectra in external electric and magnetic fields, as well as by inducing electroluminescence at low temperatures. We identify qualitatively different types of quantum emitters and classify them according to the dominant electron-hole recombination paths, determined by the mechanisms of intervalley mixing occurring in fundamental conduction and/or valence subbands.

Phosphor-free micro-pyramid InGaN-based white light-emitting diode with a high color rendering index on a β-Ga2O3 substrate.

We demonstrate the InGaN/GaN-based monolithic micro-pyramid white (MPW) vertical LED (VLED) grown on (-201)-oriented β-Ga2O3 substrate by selective area growth. The transmission electron microscopy (TEM) reveals an almost defect-free GaN pyramid structure on (10-11) sidewalls, including stacked dual-wavelength multi-quantum wells (MQWs). From the electroluminescence (EL) spectra of the fabricated MPW VLED, a white light emission with a high color rendering index (CRI) of 97.4 is achieved. Furthermore, the simulation shows that the light extraction efficiency (LEE) of the MPW VLED is at least 4 times higher compared with the conventional planar LED. These results show that the MPW VLED grown on β-Ga2O3 has great potential for highly efficient phosphor-free white light emission.

Impact of the diameter of airflow passing holes between curved microchannels on the cooling process of a vertical LED using nanofluid: DPM two-phase simulations

In this paper, a circular heatsink (HSK) with a new geometry cooled by nanofluids (NFs) flow and free airflow is numerically examined to reduce the temperature of an LED. The HSK has a number of curved microchannels (MCH) in which alumina/water NFs flows. A number of holes with different diameters are installed on the heatsink. NFs flow is simulated using the two-phase discrete phase model (DPM) and equations are solved utilizing the finite element method (FEM). The results demonstrate that an enhancement in the curvature of the MCH can reduce the average HSK temperature (THS) by 2.34 degrees, and an increment in the radius of the MCH intensifies the maximum THS (T-max) by about 3 degrees. The use of models M1 and M3 leads to the highest and lowest T-max, respectively. The use of a MCH with greater curvature can improve the thermal coefficient by 6.4%. The T-max uniformity in the HSK corresponds to model M3 with a MCH radius (MCR) of 12 cm, and the minimum temperature (T-min) uniformity is related to model M1 with a MCR of 4 cm. Increasing the radius of MCHs from 4 to 12 cm reduces the pressure drop (Δp) by 44.8%.

Surface Defect Suppression for High Color Purity Light‐Emitting Diode of Free‐Standing Single‐Crystal Perovskite Film

AbstractHigh color purity is one of the important features for single‐crystal metal halide perovskite light‐emitting diode (LED). Despite single‐crystal perovskite showing low bulk defect concentration, single‐crystal perovskite LEDs do not exhibit high color purity advantage due to the absence of effective surface defect passivation. Herein, one fully wrapped structure is proposed to passivate the surface of the free‐standing CsPbBr3 single‐crystal films. The surface of CsPbBr3 single‐crystal films is wrapped by ultra‐thin polymethyl methacrylate, precisely controlling the thickness. The single‐crystal perovskite film device can achieve high color purity with a full width at half maximum (FWHM) of 15.8 nm) and a large luminescent area of 2.25 mm2. It is observed that surface passivation is due to interaction of CO bond in polymer chains with the Lewis acid PbBr2. The passivated perovskite single‐crystal films significantly improve carrier lifetime and suppress surface defects. It is noteworthy that the passivated free‐standing single‐crystal perovskite films are feasible to build up a vertical LED device structure, avoiding the edge glowing and short‐circuiting of the LED device. This study demonstrates the large luminescent area of the high‐quality millimetre‐scale free‐standing single‐crystal films for wide color gamut display and vertical optoelectronic devices.

An Ultra-thin Vertical Deep Ultraviolet LED Realized by Epilayer Transfer

AlGaN 基深紫外（Deep ultraviolet，DUVï¼‰å‘å ‰äºŒæžç®¡ï¼ˆLight⁃emitting diode，LEDï¼‰å¯ç”¨äºŽæ€èŒã€æ°´ä½“å‡€åŒ–ã€å ‰ç–—ã€å›ºåŒ–ã€ä¼ æ„Ÿå’Œéžè§†è·é€šä¿¡ç­‰åœºåˆï¼Œåœ¨ç”Ÿç‰©ã€çŽ¯å¢ƒã€å·¥ä¸šã€åŒ»ç–—å’Œå†›äº‹ç­‰é¢†åŸŸå ·æœ‰å¹¿é˜”çš„åº”ç”¨å‰æ™¯ã€‚é’ˆå¯¹çŽ°é˜¶æ®µ DUV LED å¤–é‡å­æ•ˆçŽ‡è¾ƒä½Žçš„é—®é¢˜ï¼Œæœ¬æ–‡æå‡ºäº†ä¸€ç§è¶ è–„åž‚ç›´ç»“æž„çš„ DUV LED æ–¹æ¡ˆã€‚è¯¥æ–¹æ¡ˆåŸºäºŽè“å®çŸ³â€ç¡ æ™¶åœ†é”®åˆå’Œç‰©ç†å‡è–„å·¥è‰ºå®žçŽ°äº†é«˜è´¨é‡ DUV LED å¤–å»¶å±‚ä»Žè“å®çŸ³è¡¬åº•åˆ°é«˜å¯¼çƒ­ç¡ åŸºæ¿çš„è½¬ç§»ï¼Œå¹¶é‡‡ç”¨è½¬ç§»åŽäºšå¾®ç±³åŽšåº¦çš„è¶ è–„å¤–å»¶å±‚åˆ¶å¤‡å‡ºåž‚ç›´ç»“æž„çš„ AlGaN DUV LEDã€‚å™¨ä»¶çš„å‡ºå ‰é¢åœ¨å‡è–„å·¥è‰ºåŽæ— éœ€ç‰¹æ®Šçš„åŒ–å­¦å¤„ç†ä¾¿å¯å®žçŽ°çº³ç±³çº§çš„ç²—åŒ–ï¼Œé åˆè¶ è–„å¤–å»¶å±‚ç»“æž„å ·å¤‡æ˜¾è‘—çš„å¤±è°å¾®è ”æ•ˆåº”ï¼Œæœ‰åŠ©äºŽç ´åé«˜é˜¶æ³¢å¯¼æ¨¡å¼ï¼Œä»Žè€Œå¢žåŠ TM æ³¢çš„å‡ºå ‰å¹¶æå‡å™¨ä»¶çš„å‡ºå ‰æ•ˆçŽ‡ã€‚æµ‹è¯•è¡¨æ˜Žï¼Œè½¬ç§»åŽçš„å¤–å»¶å±‚åŽšåº¦çº¦ä¸º 710 nm，制备出的 DUV LED å‘å ‰å ‰è°±å³°å€¼æ³¢é•¿çº¦ä¸º 271 nm。该垂直结构 DUV LED 制备方案为实现高效 DUV å ‰æºæä¾›äº†å¯è¡Œè·¯å¾„ã€‚

Performance improvement of AlGaInP based red LEDs by combination of omnidirectional mirror and AuZn micro-contacts

An omnidirectional reflector (ODR) consisted of (MgF2)/Ag was employed in AlGaInP-based vertical red light-emitting diodes (LEDs) in order to increase the light extraction hence the wall-plug efficiency. In this structure, the dielectric MgF2 layer with low refractive index acted as current blocking and reflection enhancing layer. The cylindrical AuZn alloy micro-contacts perforated through the MgF2 layer and played roles in current spreading and injection. The area ratio of AuZn micro-contacts was optimized to improve the performance of the LED. The results indicated that increasing the area ratio of micro-contacts led to the improvement of current injection uniformity and reduction of forward voltage especially at higher injection current, but at the expense of light extraction by reducing reflection. After optimized, the best performance of red-light LEDs can be obtained with 3% area ratio of micro-contacts.

High Efficiency and Uniform Emission in Micropixelated Inorganic/Organic Hybrid Vertical Light-Emitting Transistors and Displays

Vertical light-emitting transistors (VLETs) fabricated by integrating organic vertical transistors and organic light-emitting diodes (OLEDs) have been proposed as a prospective building block for display technologies. However, organic vertical transistors normally have non-ohmic injection and a low-mobility channel, resulting in low VLET performance compared to the pristine OLED. The difficulty of fine patterning the source electrode and organic layer in a stacked VLET geometry has also been a technical issue limiting industrial applications. This paper reports on a simple approach to realize a high-performance, miniaturized VLET by using a highly conductive, well-designed inorganic transistor. Here, we investigate the ZnO transistor configured with an insulator-encapsulated source electrode to confine the current pathway in the VLET, which can be easily fabricated and integrated with various solution-processed or vacuum-sublimed inverted OLEDs (IOLEDs). This ZnO transistor exhibits ohmic contact and a high electron mobility of >10 cm2/(V s) that enables effective electron injection and lateral transport in the VLET, forming a millimeter-scale density gradient (channel depth) for strong surface emission. Furthermore, the high mobility of ZnO facilitates the design of a simple source pattern with a large aperture ratio on the ZnO area to control the current density and distribution and thus the VLET output. From a systematic study of the source design, we show that the ZnO transistor can be optimized to achieve homogeneously high conductivity in the ON state and yield the best VLET performance with maximum emission intensity and efficiency close to those of the IOLED, while the emission can be spatially uniform and precisely defined by the ZnO pattern. Finally, we implement a micropixelated VLET-based active matrix panel to demonstrate the prospect of high-resolution display applications.

Molecular Beam Epitaxy of AlGaN Epilayers on Si for Vertical Deep Ultraviolet Light-Emitting Diodes

Silicon (Si) has been an appealing substrate for vertical aluminum gallium nitride (AlGaN) deep ultraviolet (UV) light-emitting diodes (LEDs), toward which, the first step is to demonstrate AlGaN deep UV LEDs on Si. Nonetheless, the epitaxy of AlGaN epilayers on Si remains a challenge. Herein, we demonstrate the molecular beam epitaxy of AlGaN epilayers on Si using a nanowire-based template over a wide Al content range from 35%–70%. Smooth AlGaN surface down to a rms roughness of 0.4 nm is obtained using this approach. Vertical AlGaN deep UV LEDs emitting down to 247 nm are also demonstrated.

(Invited) III-Oxide/III-Nitride Heterostructures for Power Electronics and Optoelectronics Applications

Due to their large bandgap, high critical electric field, and availability of high-quality large-size melt-grown bulk substrates, III-oxides including Ga2O3, Al2O3, In2O3, and their alloys have been extensively investigated for a myriad of electronic and optoelectronic applications. Recently, β-Ga2O3 based power electronics, RF transistors, and ultraviolet (UV) photodetectors have been demonstrated with promising performance. However, p-type β-Ga2O3 is still elusive due to high dopant activation energy (>1 eV), large hole effective mass, and hole trapping. This significantly limits the design freedom for β-Ga2O3 devices. Other p-type semiconductors have been proposed to form heterostructures with β-Ga2O3 such as p-NiO, p-Cu2O, and p-type III-nitrides. As popular wide bandgap semiconductors, III-nitrides are promising candidates to form III-oxide/III-nitride heterostructures to enable advanced device structures and new functionalities. Furthermore, III-oxides and III-nitrides can be epitaxially grown on each other with small lattice mismatch (< 5% for GaN and β-Ga2O3) by the industrial standard epitaxial method MOCVD. For example, vertical GaN violet LEDs grown on n-type β-Ga2O3 substrates have been reported. This talk will present our recent work on III-oxide/III-nitride heterostructures in power electronics and optoelectronics.For power electronics, β-Ga2O3/GaN p-n heterojunctions will first be discussed. The heterojunction via mechanical exfoliation shows decent forward rectifying behaviors and thermal stability up to 200 °C but relatively low breakdown voltages (BV). To improve the breakdown capability, we carried out a comprehensive TCAD simulation study to design mesa edge termination for kV-class β-Ga2O3/GaN p-n heterojunctions. It was found that the electric field crowding effect is the main reason for the low BV. Several mesa edge termination structures were investigated such as deeply-etched mesa, step mesa, and p-GaN guard ring. Second, normally-off AlN/β-Ga2O3 field-effect transistors using polarization-induced doping will be discussed. A large two-dimensional electron gas is formed at the AlN/β-Ga2O3 interface due to polarization effects, and p-GaN gate is used to realize tunable positive threshold voltage. The device transfer and output characteristics with different device structures are also studied. For optoelectronics applications, self-powered spectrally distinctive Ga2O3/GaN heterojunction UV photodetectors grown by MOCVD will be discussed. Opposite current polarities are observed under different illumination wavelengths due to different carrier transports, which can be utilized to distinguish different spectra. These results indicate that (ultra)wide bandgap III-oxide/III-nitride heterostructures are a promising platform to enable new device structures and functionalities.

3.76-Gbps yellow-light visible light communication system over 1.2 m free space transmission utilizing a Si-substrate LED and a cascaded pre-equalizer network.

Recently, visible light communication (VLC) has emerged as a promising communication method in 6G. To achieve 6G high-speed transmission, wavelength division multiplexing (WDM) based VLC systems are a highly promising candidate. However, the "yellow and green gap" greatly limits the yellow light efficiency of InGaN-based LEDs and also restricts the transmission rate of yellow LEDs. In addition, pre-equalization and post-equalization also have an important impact on high-speed communication. In this paper, we propose to employ a vertical InGaN-based Si-substrate yellow LED with bit-power loading discrete multitone (DMT) modulation and a novel cascaded pre-equalizer network to achieve a high-speed yellow-light VLC system. The proposed cascaded pre-equalizer network is based on a digital Zobel network and a partial nonlinear pre-equalizer (DZNPN). The microscopic time-domain transient response of the high-speed and large-amplitude signal is also investigated to show a severe impairment. Utilizing the DZNPN cascaded pre-equalizer network based on the third-order Volterra series, a record-breaking data rate of 3.764Gbps over 1.2 m free space and 3.808Gbps over 0.7 m are experimentally demonstrated under the hard decision-forward error correction (HD-FEC) threshold of 3.8 × 10-3. The rate can be improved from 2.818Gbps to 3.764Gbps with 650Mbaud compared to the un-preprocessed signal. This is the highest data rate ever reported for yellow-light VLC systems based on a single LED to the best of our knowledge.

Three dimensional truncated-hexagonal-pyramid vertical InGaN-based white light emitting diodes based on β-Ga2O3.

In this Letter, we describe the fabrication of three dimensional (3D) truncated-hexagonal-pyramid (THP) vertical light emitting diodes (VLEDs) with white emission grown on β-Ga2O3 substrate. In the 3D n-GaN layer, it is noted that the longitudinal growth rate of the 3D n-GaN layer increases as the flow rate of N2 decreases and H2 increases. Moreover, the 3D THP VLED can effectively suppress the quantum-confined Stark effect (QCSE) compared with planar VLEDs due to the semipolar facets and strain relaxation. Thus, the internal quantum efficiency (IQE) of the 3D THP VLED has been doubled and the V-shaped pits have been greatly reduced. In particular, the 3D THP VLED enables multi-wavelength emission (448.0 nm and 498.5 nm) and also shows better light extraction efficiency (LEE), which presents an effective way for the realization of phosphor-free white LED devices.

Mobility test to assess functional vision in dark-adapted patients with Leber congenital amaurosis

BackgroundInherited retinal degenerations (IRDs) affect daylight and night vision to different degrees. In the current work, we devise a method to quantify mobility under dark-adapted conditions in patients with severe childhood blindness due to Leber congenital amaurosis (LCA). Mobility thresholds from two different LCA genotypes are compared to dark-adapted vision measurements using the full-field stimulus test (FST), a conventional desktop outcome measure of rod vision.MethodsA device consisting of vertical LED strips on a plane resembling a beaded curtain was programmed to produce a rectangular pattern target defining a ‘door’ of varying luminance that could appear at one of three positions. Mobility performance was evaluated by letting the subject walk from a fixed starting position ~ 4 m away from the device with instructions to touch the door. Success was defined as the subject touching within the ‘door’ area. Ten runs were performed and the process was repeated for different levels of luminance. Tests were performed monocularly in dark-adapted and dilated eyes. Results from LCA patients with the GUCY2D and CEP290 genotypes and normal subjects were analyzed using logistic regression to estimate the mobility threshold for successful navigation. The relation of thresholds for mobility, FST and visual acuity were quantified using linear regression.ResultsNormal subjects had mobility thresholds near limits of dark-adapted rod vision. GUCY2D-LCA patients had a wide range of mobility thresholds from within 1 log of normal to greater than 8 log abnormal. CEP290-LCA patients had abnormal mobility thresholds that were between 5 and 6 log from normal. Sensitivity loss estimates using FST related linearly to the mobility thresholds which were not correlated with visual acuity.ConclusionsThe mobility task we developed can quantify functional vision in severely disabled patients with LCA. Taken together with other outcome measures of rod and cone photoreceptor-mediated vision, dark-adapted functional vision should provide a more complete understanding of the natural history and effects of treatment in patients with LCA.

Vertical AlGaN Deep Ultraviolet Light Emitting Diodes with Polarization Enhanced p-AlGaN Epilayer on Si Substrate

Despite of the technological importance of developing AlGaN deep UV LEDs on Si, there are only a few reports about AlGaN deep UV LEDs on Si based on AlGaN epilayers. Herein, we show vertical AlGaN deep UV LEDs on Si with polarization enhanced p-AlGaN epilayer. The devices emit at 278 nm, with uniform current injection. Compared to devices using standard p-AlGaN epilayer, the series resistance of devices with polarization enhanced p-AlGaN epilayer is reduced by a factor of 5. This work represents the first report of AlGaN deep UV LEDs on Si with polarization enhanced p-AlGaN epilayers.

Self-Assembled Size-Tunable Microlight-Emitting Diodes Using Multiple Sapphire Nanomembranes.

Microlight-emitting diode (Micro-LED) is the only display production technology capable of meeting the high-performance requirements of future screens. However, it has significant obstacles in commercialization due to etching loss and efficiency reduction caused by the singulation process, in addition to expensive costs and a significant amount of time spent on transfer. Herein, multiple-sapphire nanomembrane (MSNM) technology has been developed that enables the rapid transfer of arrays while producing micro-LEDs without the need for any singulation procedure. Individual micro-LEDs of tens of μm size were formed by the pendeo-epitaxy and coalescence of GaN grown on 2 μm width SNMs spaced with regular intervals. We have successfully fabricated micro-LEDs of different sizes including 20 × 20 μm2, 40 × 40 μm2, and 100 × 100 μm2, utilizing the membrane design. It was confirmed that the 100 × 100 μm2 micro-LED manufactured with MSNM technology not only relieved stress by 80.6% but also reduced threading dislocation density by 58.7% compared to the reference sample. It was proven that micro-LED arrays of varied chip sizes using MSNM were all transferred to the backplane. A vertical structure LED device could be fabricated using a 100 × 100 μm2 micro-LED chip, and it was confirmed to have a low operation voltage. Our work suggests that the development of the MSNM technology is promising for the commercialization of micro-LED technology.

Vertical semiconductor deep ultraviolet light emitting diodes on a nanowire-assisted aluminum nitride buffer layer

Vertical light-emitting diodes (LEDs) have many advantages such as uniform current injection, excellent scalability of the chip size, and simple packaging process. Hitherto, however, technologically important semiconductor aluminum gallium nitride (AlGaN) deep ultraviolet (UV) LEDs are mainly through lateral injection. Herein, we demonstrate a new and practical path for vertical AlGaN deep UV LEDs, which exploits a thin AlN buffer layer formed on a nanowire-based template on silicon (Si). Such a buffer layer enables in situ formation of vertical AlGaN deep UV LEDs on Si. Near Lambertian emission pattern is measured from the top surface. The decent reflectivity of Si in the deep UV range makes such a configuration a viable low-cost solution for vertical AlGaN deep UV LEDs. More importantly, the use of such a thin AlN buffer layer can allow an easy transfer of device structures to other carrier wafers for vertical AlGaN deep UV LEDs with ultimately high electrical and optical performance.

AlGaN nanowire deep ultraviolet light emitting diodes with graphene electrode

Despite graphene being an attractive transparent conductive electrode for semiconductor deep ultraviolet (UV) light emitting diodes (LEDs), there have been no experimental demonstrations of any kind of semiconductor deep UV LEDs using a graphene electrode. Moreover, although aluminum gallium nitride (AlGaN) alloys in the format of nanowires are an appealing platform for surface-emitting vertical semiconductor deep UV LEDs, in particular, at short wavelengths, there are few demonstrations of AlGaN nanowire UV LEDs with a graphene electrode. In this work, we show that transferred graphene can serve as the top electrode for AlGaN nanowire deep UV LEDs, and devices emitting down to around 240 nm are demonstrated. Compared to using metal, graphene improves both the light output power and external quantum efficiency. Nonetheless, devices with a graphene electrode show a more severe efficiency droop compared to devices with metal. Here, we attribute the heating effect associated with the large contact resistance to be the major reason for the severe efficiency droop in the devices with a graphene electrode. Detailed scanning electron microscopy and Raman scattering experiments suggest that the nanowire height nonuniformity is the main cause for the large contact resistance; this issue could be potentially alleviated by using nanowires grown by selective area epitaxy that is able to produce nanowires with uniform height. This work, therefore, not only demonstrates the shortest wavelength LEDs using a graphene electrode but also provides a viable path for surface-emitting vertical semiconductor deep UV LEDs at short wavelengths.

Fabrication of vertical AlGaN-based deep-ultraviolet light-emitting diodes operating at high current density (∼43 kA cm−2) using a laser liftoff method

We have successfully fabricated vertical LEDs by separating a 1 × 1 cm2 wafer composed of deep-ultraviolet LED on a sapphire substrate from the substrate using a laser liftoff (LLO) method. Reproducible substrate separation was achieved by the LLO method using an Al0.68Ga0.32N underlayer film on an AlN template with periodic pillars. The fabricated vertical LED successfully demonstrated notable luminescence (peak wavelength: 298 nm) characteristics up to a current density of ∼43 kA cm−2 at room temperature and in pulsed drive, which is expected to be used in high-power LEDs and laser diodes.

A vertical AlGaN DUV light-emitting diode fabricated by wafer bonding and sapphire thinning technology

We demonstrate a vertical AlGaN DUV LED with an emission wavelength of 272 nm and submicron thickness. The device epilayers’ thickness is reduced to ∼670 nm by a combination of wafer bonding and thinning techniques, and this results in the thinnest vertical DUV LED reported to date. A light-emitting surface with a root mean square value of 74.7 nm is also induced by the thinning process without any other surface-roughing treatments. An n-contact electrode with a mesh geometry is adopted to expose the emission region, while the bottom metal electrode functions as a reflector to reflect downward-propagating light in an upward direction.

A comprehensive study of current-crowding effect in high power vertical AlInGaN LEDs under high pulsed current

The goal of the study is examination of current-crowding effect in high power AlInGaN LEDs. This effect was presented by mapping of EL (electroluminescence) near filed under high pulse current. LED chip of vertical design was study in high range of current (10−9 ÷ 70A). This operating mode of LEDs are interesting for different applications, such as pumping lasers, VLC and LiFi, as well as for investigation accelerated degradation process of LEDs.