Effect of Mg Doping in GaN Interlayer on the Performance of Green Light-Emitting Diodes

Zhang, Jun; Xiang-Jing, Zhuo; Li, Danwei; Yu, Lei; Li, Kai; Zhang, Yuanwen; Diao, Jia-Sheng; Wang, Xingfu; Li, Shuti

doi:10.1109/lpt.2014.2362939

Cited by 10 publications

(6 citation statements)

References 17 publications

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“…As the injection current increased from 0.01 to 350 mA, these samples showed a significant efficiency droop: the To evaluate the effect of the LT p-GaN layer on the efficiency droop in these three samples, the integrated EL intensity divided by the current, i.e., relative EQE, was plotted as a function of the injection current at 300 K, as shown in Figure 7. As the injection current increased from 0.01 to 350 mA, these samples showed a significant efficiency droop: the EQE first increased due to the gradual saturation of nonradiative recombination centers and then decreased (i.e., efficiency droop), mainly due to electron leakage [19,20]. To qualitatively compare the efficiency droop for the three samples, efficiency droop can be defined as follows:…”

Section: Resultsmentioning

confidence: 99%

“…Generally, efficiency droop is caused by two main factors: (i) a high content of In can generate structural defects acting as nonradiative recombination centers due to a large discrepancy in atomic size between indium (In) and gallium (Ga), and a large lattice mismatch of 11% between InN and GaN; (ii) a large lattice mismatch between the InGaN well layer with a high In content and the GaN barrier layer causes straininduced polarization, resulting in a strong quantum-confined Stark effect (QCSE) [15][16][17]. Previous studies showed that the introduction of a low-temperature (LT) p-GaN layer effectively improved the EL characteristics and reduced the efficiency droop in GaN-based blue LEDs [18][19][20][21]. Nevertheless, the effect of an LT p-GaN layer on longer-wavelength GaN-based LEDs has not been reported in detail, especially with different thicknesses of the LT p-GaN layer.…”

Section: Introductionmentioning

confidence: 99%

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Optical Properties of GaN-Based Green Light-Emitting Diodes Influenced by Low-Temperature p-GaN Layer

Jian-fei

Chen

et al. 2021

Nanomaterials

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GaN-based green light-emitting diodes (LEDs) with different thicknesses of the low-temperature (LT) p-GaN layer between the last GaN barriers and p-AlGaN electron blocking layer were characterized by photoluminescence (PL) and electroluminescence (EL) spectroscopic methods in the temperature range of 6–300 K and injection current range of 0.01–350 mA. Based on the results, we suggest that a 20 nm-thick LT p-GaN layer can effectively prevent indium (In) re-evaporation, improve the quantum-confined Stark effect in the last quantum well (QW) of the active region, and finally reduce the efficiency droop by about 7%.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optical Properties of GaN-Based Green Light-Emitting Diodes Influenced by Low-Temperature p-GaN Layer

Jian-fei

Chen

et al. 2021

Nanomaterials

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“…Nevertheless, the need for efficient emitters in this spectral region is well acknowledged and has prompted intensive efforts in this direction, leading to optimizations of growth conditions, improvements to structure design and the use of alternative substrates among other techniques. For instance, the crystalline quality of high In-content QWs is improved by growing on nanorod-patterned GaN/Si templates, while the IQEs can be increased by controlling the growth temperatures to reduce point defect incorporation. , The introducing of interlayer and electron blocking layer also leads to a smoother band diagram and more uniform carrier distributions which enhances electroluminescence; , on the other hand, light output powers can be boosted with high-density ultrasmall In-rich quantum dots with good carrier confinement and reduced defects . The proposed device structure will benefit significantly from the success of these efforts.…”

Section: Resultsmentioning

confidence: 99%

Monolithic Broadband InGaN Light-Emitting Diode

2016

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A monolithic non-phosphor broadband-emission light-emitting diode is demonstrated, comprising a combination of high-density micro-structured and nano-structured InGaN-GaN quantum wells fabricated using a top-down approach. Broadband emission is achieved by taking advantage of low-dimensional-induced strain-relaxation of highly-strained quantum wells, combining light emitted from strain-relaxed nano-tips at wavelengths shorter than the as-grown by as much as 80 nm with longer-wavelength light emitted from the larger non-relaxed microdisks. The localized emission characteristics have been studied by spatially-resolved near-field photoluminescence spectroscopy which enabled both the photoluminescence intensity and spectrum from individual nano-tips to be distinguished from emission at the larger-dimensioned regions. Distinctive blue-green-yellow emission can be observed from the electroluminescent device, whose continuous broadband spectrum is characterized by CIE coordinates of (0.39, 0.47) and color rendering index of 41. Emission can be tuned by adjusting the relative densities of nano-tips and microdisks along the linear color gamut defined by their respective CIE coordinates.temperatures so that their emission spectra are shifted away from the visible to the infrared regions. Fluorescent lamps, on the other hand, are based on mercury gas discharges which emit predominantly at discrete wavelengths in the ultraviolet. White light is be generated through color conversion using color-converters such as phosphors, producing a combined spectrum consisting of a mixture of broad and line emissions. In both cases, the lamps do not emit directly or entirely in the visible region which is useful for illumination, thus compromising on their efficiencies. Such wastage of non-visible spectral components can be avoided by using light-emitting diodes (LEDs) which inherently are monochromatic sources with spectral line-widths in the range of 20 to 50nm.[(1), (2)] However, such widths are insufficiently broadband to cover the entire visible spectral range. Use of phosphors [(3), (4)] in combination with LEDs, analogous to the role of phosphors in fluorescent lamps, is the primary strategy towards achieving broader band emissions. LEDs based on the widebandgap GaN materials are particularly suitable for this purpose due to their abilities to emit at the shorter visible wavelengths with high efficiencies. Together with phosphors such as Ce-doped YAG which typically fluoresce in the yellow color bands, white light can be generated, albeit with spectral incompleteness. Such LED-phosphor solutions have now become commercialized products, but can hardly be regarded ideal white light sources. The large Stokes shifts of nearly 100 nm give rise to significant energy losses negating the efficiencies of the LEDs, not to mention lifetimes and environmental impacts associated with the phosphors.[(5), (6), (7)] The ideal LED-based white light source should thus be monolithic and produce a continuous spectrum across the visible band without co...

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“…These methods have brought blue InGaN/GaN LEDs with remarkable progress in IQE exceeding 80%. However, InGaN/GaN green LEDs with a high In content (25% green and 18% for blue) suffer a lower EQE than blue InGaN/GaN LEDs because of the “green gap” problem caused by the large difference in lattice constant and thermal expansion coefficient between high-In-content InGaN and GaN [ 11 , 12 ]. Several techniques such as deposition of Si-doped graded superlattice or InGaN/GaN superlattice between n-GaN and InGaN/GaN active region [ 1 , 13 ], low-temperature-grown GaN cap layer [ 14 ], and AlGaInN/GaN MQWs [ 15 ] were used to address this issue.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Photonic-Crystal-Structured p-GaN Nanorods Fabricated by Polystyrene Nanosphere Lithography Method to Improve the Light Extraction Efficiency of InGaN/GaN Green Light-Emitting Diodes

2021

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We fabricated the photonic-crystal-structured p-GaN (PC-structured p-GaN) nanorods using the modified polystyrene nanosphere (PS NS) lithography method for InGaN/GaN green light-emitting diodes (LEDs) to enhance the light extraction efficiency (LEE). A modified PS NS lithography method including two-times spin-coating processes and the post-spin-coating heating treatment was used to obtain a self-assembly close-packed PS NS array of monolayer as a mask and then a partially dry etching process was applied to PS NS, SiO2, and p-GaN to form PC-structured p-GaN nanorods on the InGaN/GaN green LEDs. The light output intensity and LEE of InGaN/GaN green LEDs with the PC-structured p-GaN nanorods depend on the period, diameter, and height of PC-structured p-GaN nanorods. RSoft FullWAVE software based on the three-dimension finite-difference time-domain (FDTD) algorithm was used to calculate the LEE of InGaN/GaN green LEDs with PC-structured p-GaN nanorods of the varied period, diameter, and height. The optimal period, diameter, and height of PC-structured p-GaN nanorods are 150, 350, and 110 nm. The InGaN/GaN green LEDs with optimal PC-structured p-GaN nanorods exhibit an enhancement of 41% of emission intensity under the driving current of 20 mA as compared to conventional LED.

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Effect of Mg Doping in GaN Interlayer on the Performance of Green Light-Emitting Diodes

Cited by 10 publications

References 17 publications

Optical Properties of GaN-Based Green Light-Emitting Diodes Influenced by Low-Temperature p-GaN Layer

Optical Properties of GaN-Based Green Light-Emitting Diodes Influenced by Low-Temperature p-GaN Layer

Monolithic Broadband InGaN Light-Emitting Diode

Investigation of Photonic-Crystal-Structured p-GaN Nanorods Fabricated by Polystyrene Nanosphere Lithography Method to Improve the Light Extraction Efficiency of InGaN/GaN Green Light-Emitting Diodes

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