GaN-based green laser diodes

Jiang, Lijin; Liu, Jianping; Cheng, Yong; Li, Zengcheng; Zhang, Liqun; Zhang, Shuming; Li, Deyao; Ikeda, Masao; Yang, Hui

doi:10.1088/1674-4926/37/11/111001

Cited by 95 publications

(38 citation statements)

References 75 publications

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“…Our band-gap calculations demonstrate that B x In 1.5x Ga 1-2.5x N has a tunable direct gap that spans the entire visible range. In contrast to BGaN, which transitions from direct to indirect gap for increasing B content, 39 the gap of BInGaN remains direct throughout the entire explored composition range. Figure 4 shows the calculated gap of B x In 1.5x Ga 1-2.5x N, B x Ga 1-x N, and In 1.5x Ga 1-1.5x N as a function of composition.…”

mentioning

confidence: 85%

BInGaN alloys nearly lattice-matched to GaN for high-power high-efficiency visible LEDs

Williams

Kioupakis

2017

Applied Physics Letters

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InGaN-based visible LEDs find commercial applications for solid-state lighting and displays, but lattice mismatch limits the thickness of InGaN quantum wells that can be grown on GaN with high crystalline quality. Since narrower wells operate at a higher carrier density for a given current density, they increase the fraction of carriers lost to Auger recombination and lower the efficiency. The incorporation of boron, a smaller group-III element, into InGaN alloys is a promising method to eliminate the lattice mismatch and realize high-power, highefficiency visible LEDs with thick active regions. In this work we apply predictive calculations based on hybrid density functional theory to investigate the thermodynamic, structural, and electronic properties of BInGaN alloys. Our results show that BInGaN alloys with a B:In ratio of 2:3 are better lattice matched to GaN compared to InGaN and, for indium fractions less than 0.2, nearly lattice matched. Deviations from Vegard's law appear as bowing of the in-plane lattice constant with respect to composition. Our thermodynamics calculations demonstrate that the solubility of boron is higher in InGaN than in pure GaN. Varying the Ga mole fraction while keeping the B:In ratio constant enables the adjustment of the (direct) gap in the 1.75-3.39 eV range, which covers the entire visible spectrum. Holes are strongly localized in non-bonded N 2p states caused by local bond planarization near boron atoms. Our results indicate that BInGaN alloys are promising for fabricating nitride heterostructures with thick active regions for high-power, high-efficiency LEDs.InGaN light-emitting diodes (LEDs) with an electricity-to-light conversion efficiency of ~39% provide large efficiency gains and cost reductions compared to incandescent and fluorescent light sources. 1 However, InGaN LEDs suffer from decreasing internal quantum efficiency at high currents (efficiency droop), particularly at longer wavelengths (green gap). The cause of the droop has been extensively studied, with Auger recombination identified as a major loss mechanism. 2 For equal electron and hole densities, the Auger recombination rate is equal to the carrier density cubed times a material-dependent Auger coefficient ! . Since the Auger coefficient is an intrinsic property of InGaN that does not depend strongly on composition, temperature, or strain, 3 the carrier density at a given current density must be lowered to reduce the Auger losses.Increasing the active-region volume is a straightforward approach to reduce the carrier density and hence the Auger loss, yet growth challenges limit its practicality. Devices using a single thick InGaN layer exhibit higher high-power efficiency than thinner quantum wells both for polar 4 and for semipolar 5 growth orientations. The thickness of InGaN active layers is however limited by the lattice mismatch with the underlying GaN layers, and the subsequent appearance of performance-degrading dislocations. On the other hand, the efficiency of multiple-quantum-well (MQW) structures is...

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confidence: 85%

BInGaN alloys nearly lattice-matched to GaN for high-power high-efficiency visible LEDs

Williams

Kioupakis

2017

Applied Physics Letters

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“…With these parameters, we calculate the average non-resonant saturation parameter seen by the atoms to be s=0. 17. As discussed previously, we then implement in our simulation an effective Rabi frequency Ω 12 equal to G s 2 12 , and an effective detuning of zero, guaranteeing the same average atomic population in the excited level ñ |2 in the experiment and the simulations.…”

Section: Measurementsmentioning

confidence: 99%

“…A usual choice for repumping atoms from the 3P 2 state is the transition  ( ) ( ) 5s5p P 5s5d D 3 2 3 2 at 497 nm. Unfortunately, laser diodes emitting in the green spectral range currently do not exist [17]. Light sources at 497nm are realized by frequency-doubling infrared laser diodes, which is for the 497 nm and 403 nm repumper light, respectively.…”

Section: Introductionmentioning

confidence: 99%

Comparison between 403 nm and 497 nm repumping schemes for strontium magneto-optical traps

et al. 2018

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The theoretical description of the external degrees of freedom of atoms trapped inside a magnetooptical trap (MOT) often relies on the decoupling of the evolution of the internal and external degrees of freedom. That is possible thanks to much shorter timescales typically associated with the first ones. The electronic structure of alkaline-earth atoms, on the other hand, presents ultra-narrow transitions and metastable states that makes such an approximation invalid in the general case. In this article, we report on a model based on open Bloch equations for the evolution of the number of atoms in a magneto-optical trap. With this model we investigate the loading of the strontium blue magnetooptical trap under different repumping schemes, either directly from a Zeeman slower, or from an atomic reservoir made of atoms in a metastable state trapped in the magnetic quadrupolar field. The fluorescence observed on the strong 461 nm transition is recorded and quantitatively compared with the results from our simulations. The comparison between experimental results and calculations within our model allowed to identify the existence of the decay paths between the upper level of the repumping transition and the dark strontium metastable states, which could not be explained by electric dipole transition rates calculated in the literature. Moreover, our analysis pinpoints the role of the atomic movement in limiting the efficiency of the atomic repumping of the Sr metastable states.

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“…In projection displays, comparing to the illumination by lamps, solid-state light sources including solid-state lasers and light emitting diodes (LEDs) can provide wider color gamut and longer lifetime etc. The LED technology, however, is not bright enough for high lumen projection displays, where its typical brightness is limited to about 2000 lumen [1]; laser diodes are the potential candidate for mass production in high lumen projection displays, but they currently face the problems of the high cost of green color and speckle [2,3]. With the development of gallium nitride-based materials, the price of green laser diodes is expected to reduce in the next few years [2].…”

Section: Introductionmentioning

confidence: 99%

Combination of micro-scanning mirrors and multi-mode fibers for speckle reduction in high lumen laser projector applications

Tong¹,

Shen²,

Song³

et al. 2017

Opt. Express

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In high lumen laser projectors, it is required to use laser diodes coupled to multi-mode fibers (MMFs) to obtain a high power illumination module. In this paper, we have fabricated an electromagnetic micro-scanning mirror (EM-MSM), and we have firstly demonstrated a speckle reduction method by the combination of the EM-MSM and the MMF. With the help of a condenser lens, laser beams modulated and reflected from the EM-MSM are coupled into the MMF within its acceptance angle. Because the fast scanning behavior of the EM-MSM results in the phase modulation and mode coupling among the MMF guided modes, the light intensity field distributions at the exit aperture of the MMF are changing. During the charge-coupled device (CCD) integration time, the random speckle patterns are integrated and homogenized by the CCD camera, and hence speckle is reduced. By driving the EM-MSM in raster scan, the lowest compound speckle contrast ratio at 0.0794 is obtained, where the EM-MSM half scanning angles are 0.4 ° and the optical power loss is lower than 4.5%. The demonstrated technique is compact and can endure the high power of the laser module; thus, it has a promising potential in high lumen laser projector applications.

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GaN-based green laser diodes

Cited by 95 publications

References 75 publications

BInGaN alloys nearly lattice-matched to GaN for high-power high-efficiency visible LEDs

BInGaN alloys nearly lattice-matched to GaN for high-power high-efficiency visible LEDs

Comparison between 403 nm and 497 nm repumping schemes for strontium magneto-optical traps

Combination of micro-scanning mirrors and multi-mode fibers for speckle reduction in high lumen laser projector applications

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