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Time-resolved photoluminescence measurements have been performed on Mg-doped GaN for Mg concentrations in the low- to mid-1019 cm−3. As-grown and annealed (600–675 °C) samples were studied. In the as-grown samples, the nonradiative carrier lifetime was found to be about 200 ps and nearly independent of the Mg concentration. Upon annealing, the carrier lifetimes shorten to ∼150 ps but, again, show little dependence on the annealing temperature. The analysis of possible Shockley–Read–Hall recombination centers and their behavior during doping and annealing suggests that the main nonradiative recombination center is the Mg–nitrogen vacancy complex. The weak dependence of the PL decay times on temperature indicates that carrier capture into this center has a very low potential barrier, and the nonradiative recombination dominates even at low temperatures. [ABSTRACT FROM AUTHOR]

To realize the single-surface conduction in a topological insulator, a microscale Corbino device was fabricated from a single crystal of a highly bulk-resistive topological insulator Sn0.02Bi1.08Sb0.9Te2S (Sn-BSTS). The four-terminal resistance was measured in 2 K–300 K, and it was found that the temperature dependence of the resistance of the Corbino device was clearly distinct from that of Sn-BSTS bulk samples. We showed that the unconventional behavior of the Corbino device was quantitatively understood by considering the top surface, bottom surface, and bulk as independent conduction paths in parallel. Furthermore, the current flow distribution was studied by introducing the resistance network model, which revealed that the top-surface dominant conduction was realized in a low temperature. This study demonstrates the usefulness of the Corbino geometry for transport measurement in topological insulators. [ABSTRACT FROM AUTHOR]

Metal‐polar InN quantum dots (QDs) are grown by metalorganic chemical vapor deposition at temperatures between 500 and 600 °C. Dot densities between 4 × 108 and 4 × 1010 cm−2 are observed. InN QDs exhibit room‐temperature photoluminescence (PL) with peak wavelengths from 1100 to >1550 nm. GaN cap layers grown on InN QDs have little effect on either peak PL wavelength or intensity, a step toward creating multilayer structures for InN QD devices. [ABSTRACT FROM AUTHOR]

Presents a study which examined the growth of In[sub0.22]Ga[sub0.78]N/In[sub0.06]Ga[sub0.94]N superlattices grown on gallium nitride films. Experimental details; Description of superlattice structures; Determination of the band gap of InGaN barrier and well layers.

The realization of the first high-brightness blue-light-emitting diodes (LEDs) in 1993 sparked a more than twenty-year period of intensive research to improve their efficiency. Solutions to critical challenges related to material quality, light extraction, and internal quantum efficiency have now enabled highly efficient blue LEDs that are used to generate white light in solid-state lighting systems that surpass the efficiency of conventional incandescent lighting by 15–20×. Here we discuss the initial invention of blue LEDs, historical developments that led to their current state-of-the-art performance, and potential future directions for blue LEDs and solid-state lighting. [ABSTRACT FROM AUTHOR]

Cyclic nigerosyl nigerose (CNN) is a cyclic tetrasaccharide that exhibits properties distinct from other conventional cyclodextrins. Herein, we demonstrate that treatment of B16 melanoma with CNN results in a dose-dependent decrease in melanin synthesis, even under conditions that stimulate melanin synthesis, without significant cytotoxity. The effects of CNN were prolonged for more than 27 days, and were gradually reversed following removal of CNN. Undigested CNN was found to accumulate within B16 cells at relatively high levels. Further, CNN showed a weak but significant direct inhibitory effect on the enzymatic activity of tyrosinase, suggesting one possible mechanism of hypopigmentation. While a slight reduction in tyrosinase expression was observed, tyrosinase expression was maintained at significant levels, processed into a mature form, and transported to late-stage melanosomes. Immunocytochemical analysis demonstrated that CNN treatment induced drastic morphological changes of Pmel17-positive and LAMP-1–positive organelles within B16 cells, suggesting that CNN is a potent organelle modulator. Colocalization of both tyrosinase-positive and LAMP-1–positive regions in CNN-treated cells indicated possible degradation of tyrosinase in LAMP-1–positive organelles; however, that possibility was ruled out by subsequent inhibition experiments. Taken together, this study opens a new paradigm of functional oligosaccharides, and offers CNN as a novel hypopigmenting molecule and organelle modulator. [ABSTRACT FROM AUTHOR]

In this work, secondary ion mass spectroscopy was used to study carbon and oxygen impurity incorporation in N-polar [000–1] GaN films grown by MOCVD. The effects of growth temperature, V/III ratio, and precursor flows were studied within a regime relevant to low temperature (In,Ga)N:Mg growth for device structures containing high indium concentrations. For films grown without magnesium, oxygen levels were between 3 and 8×10 16 cm −3 and did not depend strongly on the growth conditions. Mg-doped films yielded higher oxygen concentrations ranging from 8×10 16 to 4×10 17 cm −3 depending on the gallium and magnesium precursor flow rates. The carbon concentration in the films varied significantly with different growth conditions, and was most affected by the growth temperature and the V/III ratio. With careful tuning of the growth parameters carbon and oxygen concentrations of 2 and 4×10 16 cm −3 , respectively, were achievable under a wide range of conditions. [ABSTRACT FROM AUTHOR]

Presents information on a study which fabricated high-brightness InGaN/AlGaN double-heterostructure blue-green-light-emitting diodes. Discussion of the room-temperature Hall and photoluminescence measurements performed on InGaN films grown on GaN films; Electroluminescence spectra; Growth of InGaN films by the two-flow metalorganic chemical vapor deposition method.

The present study explores the application of sulfate radical based advanced oxidation process for the degradation of anatoxin-a. Peroxymonosulfate (PMS) was used as the source of sulfate radicals. λ = 260 nm was found to be the most effective wavelength for the activation of PMS. At pH = 6.4, initial conc. of anatoxin-a = 1.5 μM, λ = 260 nm, [PMS]/[anatoxin-a] = 100:1 and temperature = ambient, the degradation of anatoxin-a was found to be 98.6%. Radical scavenging study revealed that sulfate radicals were the dominant oxidative radicals in the degradation of anatoxin-a. The presence of carbonate and bicarbonate ions in the solution mixture had negative effect on the degradation of anatoxin-a. At low concentrations (0.2 and 2 mg/L), humic acid enhanced the degradation of anatoxin-a through photosensitization effect. However at higher concentration of humic acid, the degradation of anatoxin-a was hampered. UV/PMS/Cu 2+ system was found to be more efficient in degradation of anatoxin-a in comparison to UV/PMS/Fe 3+ system. With UV/PMS/Cu 2+ system, the degradation of anatoxin-a reached more that 99% in 10 min of irradiation time. Due to the presence of high concentration of transition metal ions and humic substance in lake water, the degradation of anatoxin-a was more in lake water in comparison to tap water. The results of this study suggests that UV-C/PMS advanced oxidation process is very efficient in the degradation of anatoxin-a, even in natural water bodies. [ABSTRACT FROM AUTHOR]

Ammonothermal growth of nitrides occurs at temperatures in excess of 800 K and pressures greater than 150 MPa. For this region, no experimentally verified equation of state (EOS) exists for ammonia, nor is there any accurate description available for the equilibrium constant of the ammonia decomposition reaction for pressures in excess of 100 MPa. To fill this void, experimental P -v- T data was collected for pure ammonia at T > 700 K and compared to extrapolated data from the reference EOS for ammonia. For the extrapolated region, the reference EOS provided excellent agreement to within error of the collected experimental data. A simplified EOS based on the Beattie–Bridgeman (BB) EOS was derived and fit to calculated and, for ammonia, extrapolated reference EOS data for ammonia, hydrogen, and nitrogen ( T < 1000 K, P < 300 MPa). By applying mixing rules with separated contributions for polar and non-polar interactions, an EOS was derived for NH 3 –N 2 –H 2 mixtures. With these expressions, an accurate description for the equilibrium constant for the ammonia decomposition reaction as a function of pressure and temperature was derived and verified against experimental data determined for total system pressures of 92, 151 and 210 MPa at T ∼810 K. Coupling of the EOSs with the equilibrium constant permitted accurate modeling of a sealed autoclave filled with pure ammonia, after incorporating corrections for the expansion of the internal free volume due to thermal expansion and elastic strain response of the autoclave walls due to internal pressure buildup. Calculated total system pressure and equilibrium ammonia density at various temperatures and initial ammonia fill densities are in very good to excellent agreement with experimental data. This paper thus provides a simple EOS for ammonia, hydrogen, nitrogen and NH 3 –N 2 –H 2 mixtures accurate to within approximately 1–2% in pressure for temperatures greater than 700 K. The equilibrium constant for the ammonia decomposition reaction includes non-ideal mixing contributions from the second virial coefficient with a resulting accuracy in the equilibrium mole fraction of ammonia of approximately 2% for T < 850 K. [ABSTRACT FROM AUTHOR]

Electron emission spectroscopy was performed on metalorganic chemical vapor deposition grown p-n−-n+ junctions with p-thicknesses ranging from 50 to 300 nm, doped with [Mg] = 3.5 × 1019 cm−3. By measuring the decreasing emitted electron intensity from a cesiated p-GaN surface with increasing p-thickness, we were able to extract the minority carrier diffusion length of electron in p-type GaN, Le = 26 ± 3 nm. The measured value is in good agreement with literature reported values. The extrapolated electron current at the n− region–p-GaN interface is in reasonable agreement with the simulated electron current at the interface. [ABSTRACT FROM AUTHOR]

The author discusses the story behind the invention of blue light-emitting diode .Topics include the progress made in combining white LED to blue LED using yellow phosphor, the material properties of indium gallium nitride as well as metal organic chemical vapor deposition as candidates for the development of blue LED and the future challenges of blue LED in the field of electronic. The author Shuji Nakamura, a Japanese physicist and the inventor of blue LED presents his autobiography.

As a step toward realizing the quantum current standard, single-electron pumping of parallel SINIS turnstiles was performed. Eleven SINIS turnstiles were fabricated on the same chip, and the number of operating SINIS turnstiles was increased one by one. As a result, 11 turnstiles were operated simultaneously up to 100 MHz, resulting in a pumped dc of 176.2 pA. We also did a linearity check toward parallelization. This paper for increasing the pumped current by parallelization will lead to practical use of stable and accurate dc sources with tiny values of the output current and the metrology triangle experiment for SI redefinition. [ABSTRACT FROM PUBLISHER]

Shuji Nakamura discovered p-type doping in Gallium Nitride (GaN) and developed blue, green, and white InGaN based light emitting diodes (LEDs) and blue laser diodes (LDs). His inventions made possible energy efficient, solid-state lighting systems and enabled the next generation of optical storage. Together with Isamu Akasaki and Hiroshi Amano, he is one of the three recipients of the 2014 Nobel Prize in Physics. In his Nobel lecture, Shuji Nakamura gives an overview of this research and the story of his inventions. [ABSTRACT FROM AUTHOR]

Shuji Nakamura discovered p-type doping in Gallium Nitride (GaN) and developed blue, green, and white 'InGaN-based' light emitting diodes (LEDs) and blue laser diodes (LDs). His inventions made possible energy efficient, solid-state lighting systems and enabled the next generation of optical storage. In this biography, Shuji Nakamura tells the story of his personal life and his scientific career. [ABSTRACT FROM AUTHOR]

A quantum electric current standard is the last missing piece of the quantum metrology triangle. A suitable candidate for realizing this quantum current standard is a single-electron pumping device based on a superconductor/insulator/normal metal/insulator/superconductor (SINIS) turnstile. Here, we show the temperature dependence of the single-electron pumped current of a SINIS turnstile. As the operating temperatures are increased, the current plateaus of the single-electron pumping tilt because of increased back tunneling, which originates from the thermal broadening of energy levels in the normal metal island of the SINIS turnstile. Hence, we find that to use a SINIS turnstile for the current standard at more than 300 mK, it is necessary to increase the superconducting energy gaps of the lead material and the charging energy of the island. [ABSTRACT FROM AUTHOR]

Confinement factor (Γ) of semipolar [formula] green laser diodes (LDs) is limited by relaxation of coherency stresses in the waveguiding heterostructure. In this paper, we demonstrate the suppression of relaxation by blocking glide of pre-existing threading dislocations using limited area epitaxy (LAE). With LAE, we show a factor of three increase in thickness before the observation of significant misfit dislocation formation for [formula] oriented In0.08Ga0.92N/GaN heterostructures. We then apply this technique to fabricate coherent AlGaN-cladding-free LDs with 73% enhanced Γ relative to planar devices without LAE, having an emission wavelength of 495 nm and threshold current density of 10.7 kA/cm2. This technique is readily applicable to AlGaN or AlInGaN cladding in addition to InGaN waveguiding layers to improve Γ of semipolar LDs. [ABSTRACT FROM AUTHOR]

We have measured the shot noise in a quantum point contact (QPC) fabricated by using InGaAs/InGaAsP heterostructure, whose conductance can be electrically tuned by the gate voltages. The reduced shot noise is observed when the QPC conductance equals to N(2e2/h) (N = 4, 5, and 6), which is the direct experimental evidence of the coherent quantized channel formation in the QPC. The deviation of the observed Fano factor from the theory is explained by the electron heating effect generated at the QPC. [ABSTRACT FROM AUTHOR]

Mesoscopic systems provide us a unique experimental stage to address nonequilibrium quantum statistical physics. By using a simple tunneling model, we describe the electron exchange process via a quantum coherent conductor between two reservoirs, which yields the fluctuation theorem (FT) in mesoscopic transport. We experimentally show that such a treatment is semiquantitatively validated in the current and noise measurement in an Aharonov-Bohm ring. The experimental proof of the microreversibility assumed in the derivation of FT is presented. [ABSTRACT FROM AUTHOR]

It has been several years since InGaN/GaN light-emitting diodes (LEDs) on nonpolar and semipolar orientations were first demonstrated. Prominent performance and inherent potential of these crystallographic orientations have been revealed as bulk-GaN substrates of arbitrary orientations became available for epitaxial device growth. At this point in time, intend to survey the progress made to date and prospect the future requirements for further device improvements. The discussion begins with a historical background: how nonpolar/semipolar orientations were introduced to III-nitride LEDs and why they are beneficial. The discussion then provides information on elementary crystallography and piezoelectricity in addition to the electronic band structure of wurtzite crystals. Later in this paper, LED reports are collected to develop comprehensive knowledge of the past research efforts and trends. Nonpolar and semipolar orientations provide not only high LED performances, e.g., optical output power and wavelength ranges, but also unique functions, e.g., polarized light emission, which will explore new fields of applications. [ABSTRACT FROM AUTHOR]

Objective: Since the existence of mouse naturally occurring CD4+CD25+ T regulatory (Treg) cells was demonstrated, a variety of human Treg subsets have been identified as distinct T cell populations. Here we show the establishment of novel Treg cell lines possessing unique characteristics. Methods: Novel Treg cell lines, designated HOZOT, were generated by coculturing human umbilical cord blood cells with mouse stromal cell lines in the absence of exogenous IL-2 or other cytokines. HOZOT were characterized and compared with CD4+CD25+ Treg cells in terms of the CD phenotype, FOXP3 expression, suppressor activity against allogeneic MLR, anergy property, and IL-10 production. Results: HOZOT were generated and expanded as normal lymphoblastoid cells with cytotoxic activity against the cocultured stromal cells. HOZOT consisted of three subpopulations as defined by phenotype: CD4+CD8+, CD4+CD8dim, and CD4−CD8+. All three subpopulations showed both suppressor and cytotoxic activities. While HOZOT''s expression of FOXP3, CD25, GITR, and cytoplasmic CTLA-4 implied a similarity to naturally occurring CD4+CD25+ Treg cells, these two Treg cells differed in IL-2 responsiveness and IL-10 production. Conclusions: Our studies introduce a new method of generating Treg cells in an IL-2-independent manner and highlight a unique Treg cell type with cytotoxic activity and a phenotype of FOXP3+CD4+CD8+CD25+. [Copyright &y& Elsevier]

Objective: In this study, we analyzed murine primitive erythropoiesis by coculturing Flk-1+ ES-derived cells with OP9 to find efficient culture conditions for erythroid cell induction. We utilized a nonserum culture system and EPO (erythropoietin) and found that this cytokine had unique properties.Materials and methods: ES cells (E14.1) were first differentiated to Flk-1+ cells and then cocultured with OP9 stromal cells. BIT9500 was used as a serum replacement. The erythroid morphology, hemoglobin types, and TER-119 expression levels were analyzed.Results: Primitive erythroid cells with embryonic hemoglobin were generated very efficiently when the serum-containing culture was converted to the nonserum system. In this serum-free culture, TER-119+ erythroblasts appeared first on day 2 and maturation proceeded until day 7. When EPO was added to this coculture, the number of induced floating cells increased twofold to threefold. Unexpectedly, the erythroid-specific antigen TER-119 expression of these cells was drastically reduced. Since reduced TER-119 expression is usually interpreted as maturation arrest, we examined the phenotypic features of the EPO-treated cells. We found, however, no evidence of maturation arrest in the aspects of morphology and hemoglobin content. EPO did not suppress TER-119 expression of erythroblasts derived from fetal liver or adult bone marrow.Conclusions: Our results showed that EPO had the unusual property of inducing TER-119- erythroblasts in ES-derived primitive erythropoiesis. It is likely that this effect is unique to primitive erythropoiesis. [Copyright &y& Elsevier]

UV InGaN and GaN single-quantum-well structure light-emitting diodes (LEDs) were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. When the emission wavelength of UV InGaN LEDs was shorter than 380 nm, the external quantum efficiency (EQE) of the LED on ELOG was much higher than that on sapphire only at high-current operation. At low-current operation, both LEDs had the same EQE. When the active layer was GaN, EQE of the LED on sapphire was much lower than that on ELOG at both low- and high-current operation due to the lack of localized energy states formed by In composition fluctuations. In order to improve the lifetime of laser diodes (LDs), ELOG had to be used because the operating current density of the LDs is much higher than that of LEDs. A violet InGaN multi-quantum-well GaN/A1GaN separate-confinement-heterostructure LD was grown on ELOG on sapphire. The LDs with cleaved mirror facets showed an output power as high as 40 mW under roomtemperature continuous-wave (CW) operation. The stable fundamental transverse mode was observed at an output power of up to 40 mW. The estimated lifetime of the LDs at a constant output power of 10 mW was more than 2,000 hours under CW operation at an ambient temperature of 60°C. [ABSTRACT FROM AUTHOR]

The recent progress in III-nitride tunnel junction (TJ) contacts for optoelectronic devices is summarized in this review paper. Due to the rapid developments of various III-nitride based optoelectronic devices for different emerging applications, TJs are of interest for these devices to achieve more efficient device performance. This review paper first briefly describes the working principles of TJs and the advantages of employing TJs in optoelectronic devices. The significant advancements in III-nitride TJs realized by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are addressed, as well as their TJ device performances. Lastly, the critical challenges for employing III-nitride TJs in wide bandgap ultraviolet (UV) light emitters are discussed for future investigations. [ABSTRACT FROM AUTHOR]

Metasurface‐based optical elements offer a wide design space for miniature and lightweight optical applications. Typically, metasurface optical elements transform an incident light beam into a desired output waveform. Recent demonstrations of light‐emitting metasurfaces highlight the potential for directly producing desired output waveforms via metasurface‐mediated spontaneous emission. In this work, reciprocal finite‐difference time‐domain (FDTD) simulations and machine learning are used to enable the inverse design of highly unidirectional photoluminescent III‐Nitride quantum well metasurfaces capable of directive p‐, s‐, or combined p‐ and s‐ polarized emission at arbitrary angles. In comparison with previous intuition‐guided designs using the same quantum well architectures, the inverse design approach enables new polarization capabilities and experimentally demonstrated improvements in directivity of 54%. An analysis of ways in which the inverse design both validates and contradicts previous intuition‐guided design heuristics is presented. Ultimately, the combination of reciprocal simulations and efficient global optimization (EGO) grants remarkable improvements in emission directivity and results in full control over the polarization and momentum of emitted light, including simultaneous directional emission of s‐ and p‐polarized light. [ABSTRACT FROM AUTHOR]

Reports on how structural imperfections in InGaN-based light-emitting diodes and laser-diodes have been utilized. How dislocations have been found to increase the threshold current density of laser diodes; Use of light-emitting diodes in displays and semiconductor laser diodes (LD); Details of the three breakthroughs in terms of InGaN films.

Deals with a study which demonstrated a continuous-wave operation of indium gallium nitride multi-quantum-well structure laser diodes at room temperature. Laser diodes grown on sapphire and spinel substrates; Emission mechanism; Summary.

Describes the expression of the DLX-7 homeobox gene in normal hematopoietic cells and leukemia cell lines with erythroid characteristics. Relation to the Drosophila distal-less (Dll) gene; Antisense oligonucleotide targeted against the translation start site; Expression in the forebrain and craniofacial structures.

High output InGaN single quantum well type blue and green light emitting diodes (LEDs) with an optical output of between 3 and 5 mW have been developed and commercialized. The differences in peak absorption energy and light emitting energy for the blue and green LEDs were 290 and 570 meV. These values indicate that the LED or laser emission is generated from a deep localized level in an InGaN well layer. An InGaN multiple quantum well laser diode was developed that oscillated continuously at room temperature for more than 300 hours. The preliminary characteristics are an output of 50 mW, an operating temperature of 100 °C, a characteristic temperature of 170 K, and an oscillation wavelength of 416 nm. © 1998 Scripta Technica, Electron Comm Jpn Pt 2, 81(5): 1–8, 1998 [ABSTRACT FROM AUTHOR]

A photoluminescence technique has been demonstrated on InGaN/GaN light-emitting diodes (LEDs) to evaluate their diode ideality factors. Selectively excited active regions produce potential differences between two contact terminals in addition to luminescence, from which the rate of recombination and terminal voltage have been related. Obtained ideality factors on commercial LEDs were between 1.1 and 2.4, which were significantly smaller than values determined via current–voltage characteristics. The ideality factor has been discussed from the viewpoint of direct-band-gap light-emitting pn junctions, and the notion that quantum-well structure takes over the role of the recombination plane introduced by the Sah–Noyce–Shockely analysis is proposed. [ABSTRACT FROM AUTHOR]

The V-defect is a naturally occurring inverted hexagonal pyramid structure that has been studied in GaN and InGaN growth since the 1990s. Strategic use of V-defects in pre-quantum well superlattices or equivalent preparation layers has enabled record breaking efficiencies for green, yellow, and red InGaN light emitting diodes (LEDs) utilizing lateral injection of holes through the semi-polar sidewalls of the V-defects. In this article, we use advanced characterization techniques such as scattering contrast transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy, x-ray fluorescence maps, and atom probe tomography to study the active region compositions, V-defect formation, and V-defect structure in green and red LEDs grown on (0001) patterned sapphire and (111) Si substrates. We identify two distinct types of V-defects. The "large" V-defects are those that form in the pre-well superlattice and promote hole injection, usually nucleating on mixed (Burgers vector b = ± a ± c) character threading dislocations. In addition, "small" V-defects often form in the multi-quantum well region and are believed to be deleterious to high-efficiency LEDs by providing non-radiative pathways. The small V-defects are often associated with basal plane stacking faults or stacking fault boxes. Furthermore, we show through scattering contrast transmission electron microscopy that during V-defect filling, the threading dislocation, which runs up the center of the V-defect, will "bend" onto one of the six { 10 1 ¯ 1 } semi-polar planes. This result is essential to understanding non-radiative recombination in V-defect engineered LEDs. [ABSTRACT FROM AUTHOR]

The efficiency of high-power operation of multiple quantum well (QW) light emitting diodes (LEDs) to a large degree depends on the realization of uniform hole distribution between the QWs. In long wavelength InGaN/GaN QW LEDs, the thermionic interwell hole transport is hindered by high GaN barriers. However, in polar LED structures, these barriers may be circumvented by the lateral hole injection via semipolar 10 1 ¯ 1 QWs that form on the facets of V-defects. The efficiency of such carrier transfer depends on the transport time since transport in the semipolar QWs is competed by recombination. In this work, we study the carrier transfer from the semipolar to polar QWs by time-resolved photoluminescence in long wavelength (green to red) LEDs. We find that the carrier transfer through the semipolar QWs is fast, a few tens of picoseconds with the estimated room temperature ambipolar diffusion coefficient of ∼5.5 cm2/s. With diffusion much faster than recombination, the hole transport from the p-side of the structure to the polar QWs should proceed without a substantial loss, contributing to the high efficiency of long wavelength GaN LEDs. [ABSTRACT FROM AUTHOR]

The large polarization barriers between the quantum wells and quantum barriers in long-wavelength GaN-based light-emitting diodes (LEDs) inhibit their performance by requiring excess driving voltages to reach standard operating current densities. Lateral injection of carriers directly into quantum wells is required to circumvent this issue. V-defects are naturally occurring inverted hexagonal defects with semipolar 10 1 ¯ 1 -plane sidewalls generated on surface depressions from threading dislocations. LEDs engineered to intentionally generate V-defects below the active region of the LED can achieve lateral carrier injection through the V-defect sidewalls and have already been able to demonstrate world record wall-plug efficiencies for LEDs in the green-red wavelengths. V-defects can be enlarged during kinetically limited growth where the growth rate of the c-plane GaN is faster than that of their sidewalls, leaving them unfilled. We report on the metal organic chemical vapor deposition growth conditions required to fill in V-defects with p-GaN during epitaxial growth of the LED post the active region. Circular transmission length measurements of Pd/Au contacts processed on p-GaN surfaces with various amounts of unfilled V-defects showed no significant difference in their sheet resistance and specific contact resistance. J–V measurements of LEDs grown with varying unfilled V-defect densities showed no significant difference in the forward bias regime. However, in the reverse bias regime, catastrophic breakdown occurred at markedly lower voltages for samples with larger unfilled V-defect densities. This suggests that unfilled V-defects may act as hotspots for device failure, and planarizing LED surfaces may help prevent early degradation of LED devices. [ABSTRACT FROM AUTHOR]

A highly relaxed InGaN buffer layer was demonstrated over a full two-inch c-plane sapphire substrate by metalorganic chemical vapor deposition. The InGaN buffer layer was grown on a 100 nm GaN decomposition stop layer with a 3 nm thick high indium composition InGaN underlayer. After thermal decomposition of the underlayer at 1000 °C, a 200 nm thick In0.04Ga0.96N buffer showed 85% biaxial relaxation measured by a high resolution x-ray diffraction reciprocal space map. When used as a pseudo-substrate for the regrowth of InGaN/InGaN multi-quantum wells, the sample showed a 75 nm red-shift in room temperature photoluminescence when compared to a co-loaded GaN template reference. The longer emission wavelength is associated with higher indium incorporation in the InGaN layers from the lessening of the compositional pulling effect caused by compressive strain. Using this technique, a simple red light emitting diode was demonstrated with an active layer growth temperature of 825 °C and a peak wavelength of 622 nm at a current density of 20 A cm−2. This work represents a unique method to relax a III-nitride based layer over a full substrate. [ABSTRACT FROM AUTHOR]

After obtaining an epitaxially laterally overgrown GaN on sapphire by the metalorganic chemical vapor deposition method, GaN growth was continued up to a thickness of 200 μm by a hydride vapor phase epitaxy method. The InGaN multi-quantum-well-structure laser diode (LD) was grown on a free-standing GaN substrate, which was obtained by removing the sapphire substrate. The LDs with cleaved mirror facets showed an output power as high as 160 mW under room-temperature continuous-wave (CW) operation. The fundamental transverse mode was observed up to an output power of 80 mW. The lifetime of the LDs at a constant output power of 5 mW was about 180 h under CW operation at an ambient temperature of 50 °C, due to a high threshold current density of 14 kA/cm2. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the emission spectra of InGaN multi-quantum-well laser diodes under continuous-wave operation at room temperature. Details on the measured peak wavelength of the laser emission; Information on the single-mode laser emission located at the periodic subband emission peak; Factors influencing the periodic subband emission peak development.

Investigates paramagnetic resonance measurements of gallium nitride-based single quantum well light emitting diodes. Factor responsible for broad resonance; Comparison between electrically-detected and electroluminescence-detected magnetic resonance; Localization of the defects.

Examines the continuous-wave operation of indium gallium nitride multi-quantum-well structure laser diodes. Determination of the threshold current and voltage of the laser diodes; Evidence for large mode hopping of the emission wavelength between quantum dot subbands; Characteristics of the emission spectra of the laser diodes.

Examines a room-temperature continuous-wave operation of indium-gallium-nitride (InGaN) multi-quantum-well-structure laser diodes (LD) with a lifetime of 24-40 minutes. Details on the threshold current and voltage of the LD; List of short-wavelength-emitting devices; Structure of the ridge-geometry InGaN multi-quantum-well LD.

Observes the longitudinal mode spectra and ultrashort pulse generation of indium gallium nitride multiquantum well structure laser diodes (InGaN MQW LD). Growth of nitride films by metalorganic chemical vapor deposition method; Electrical properties of InGaN MQW LD; Calculation of the damping constant and frequency of relaxation oscillation.

Continuous-wave (cw) operation of InGaN multi-quantum-well structure laser diodes (LDs) was demonstrated at room temperature (RT). The threshold current and voltage of the LD were 130 mA and 8 V, respectively. The threshold carrier density was 9 kA/cm2. The lifetime of the LDs under RT cw operation was 1 s due to large heat generation. Mode hopping of the emission wavelength of the LDs was observed. The average wavelength drift due to temperature increase was 0.066 nm/K between 20 and 70 °C, because of the temperature dependence of the gain profile due to band-gap narrowing of the InGaN active layer. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Continuous-wave (cw) operation of InGaN multiquantum-well-structure laser diodes (LDs) was demonstrated at 233 K. The threshold current and voltage of the LD were 210 mA and 11 V, respectively. During room-temperature cw operation, the LDs were easily broken within one second due to heat generation. At 233 K, the lifetime of the LDs was longer than 30 min, and the emission spectra could be measured under cw operation. Only a single peak was observed under cw operation with increasing forward current above the threshold current. The characteristic temperature of the threshold current of the LDs was 162 K. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

InGaN multi-quantum well (MQW) structure laser diodes (LDs) with various different cavity lengths were fabricated on sapphire substrates with (112¯0) orientation (A face). The external differential quantum efficiency was obtained as a function of the cavity length. An internal quantum efficiency of 86%, an intrinsic loss of 54 cm-1 and a threshold gain of 110 cm-1 were obtained. Measuring the pulse response of the LDs, a carrier lifetime of 2.5 ns was obtained. A threshold carrier density was calculated as 1.3×1019/cm3. The emission wavelength of the LDs was around 406 nm. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Stripe- and ridge-geometry in InGaN multi-quantum-well (MQW)-structure laser diodes (LDs) were fabricated on sapphire substrates with (112¯0) orientation (A face). The ridge-geometry InGaN MQW LDs showed strong stimulated emission at a wavelength of 411.3 nm under a pulsed current injection of 199 mA at room temperature. The differential quantum efficiency per facet and the threshold current of ridge-geometry LDs were 30% and 180 mA, respectively. The laser threshold current density was 3 kA/cm2. These values were greatly improved in comparison to those of stripe-geometry LDs. The characteristic temperature of the threshold current was around 185 K. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the growth of InGaN multi-quantum-well structure laser diodes by metalorganic chemical vapor deposition. Composition of the laser; Observation on the stimulated emission; Determination of the beam full widths at half power for the far-field radiation patterns.