Characterization of GaInN/GaN layers for green emitting laser diodes

Wetzel, Christian; Li, Yufeng; Senawiratne, J.; Zhu, Mingwei; Xia, Yong; Tomasulo, Stephanie; Persans, P. D.; Liu, Lianghong; Hanser, Drew; Detchprohm, Theeradetch

doi:10.1016/j.jcrysgro.2009.01.067

Cited by 10 publications

(3 citation statements)

References 20 publications

(19 reference statements)

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“…Assuming a total absorption in the QWs of 16% of the incident beam power, the discussed current density of 12 A/cm 2 roughly corresponds to a laser power intensity of 240 W/cm 2 (indicated by a dashed line). From this data it can be seen that similar to droop in electrical measurements, IQE drops with higher excitation density in the polar c-plane material [28]. In contrast, both, the nonpolar a-and m-plane structures show an increase of efficiency with increasing optical excitation density.…”

Section: Cie-xsupporting

confidence: 61%

Wavelength-stable rare earth-free green light-emitting diodes for energy efficiency

Wetzel¹,

Detchprohm²

2011

Opt. Express

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Solid state lighting seeks to replace both, incandescent and fluorescent lighting by energy efficient light-emitting diodes (LEDs). Just like compact fluorescent tubes, current white LEDs employ costly rare earth-based phosphors, a drawback we propose to overcome with direct emitting LEDs of all colors. We show the benefits of homoepitaxial LEDs on bulk GaN substrate for wavelength-stable green spectrum LEDs. By use of non-polar growth orientation we avoid big color shifts with drive current and demonstrate polarized light emitters that prove ideal for pairing with liquid crystal display modulators in back light units of television monitors. We further offer a comparison of the prospects of non-polar a- and m-plane growth over conventional c-plane growth.

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Section: Cie-xsupporting

confidence: 61%

Wavelength-stable rare earth-free green light-emitting diodes for energy efficiency

Wetzel¹,

Detchprohm²

2011

Opt. Express

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“…These results are substantially higher than the best IQEs obtained for InGaN/GaN LEDs based on conventional polar c-axis structures grown on sapphire, i.e. 37% at 530 nm and 15% at 555 nm [22]. The physical parameters responsible for quantum efficiency improvement in 1D heterostructures are still not fully understood.…”

Section: Introductionmentioning

confidence: 70%

Submicrometre resolved optical characterization of green nanowire-based light emitting diodes

et al. 2011

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The electroluminescent properties of InGaN/GaN nanowire-based light emitting diodes (LEDs) are studied at different resolution scales. Axial one-dimensional heterostructures were grown by plasma-assisted molecular beam epitaxy (PAMBE) directly on a silicon (111) substrate and consist of the following sequentially deposited layers: n-type GaN, three undoped InGaN/GaN quantum wells, p-type AlGaN electron blocking layer and p-type GaN. From the macroscopic point of view, the devices emit light in the green spectral range (around 550 nm) under electrical injection. At 100 mA DC current, a 1 mm2 chip that integrates around 10(7) nanowires emits an output power on the order of 10 µW. However, the emission of the nanowire-based LED shows a spotty and polychromatic emission. By using a confocal microscope, we have been able to improve the spatial resolution of the optical characterizations down to the submicrometre scale that can be assessed to a single nanowire. Detailed μ-electroluminescent characterization (emission wavelength and output power) over a representative number of single nanowires provides new insights into the vertically integrated nanowire-based LED operation. By combining both μ-electroluminescent and μ-photoluminescent excitation, we have experimentally shown that electrical injection failure is the major source of losses in these nanowire-based LEDs.

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“…For example, in 430 nm AlGaInN blue, external wall plug efficiencies up to 60% have been achieved, while 525 nm AlGaInN green hardly reaches up to 27%. 3,4 This challenge in the green is compounded by the fact of an efficiency droop, common to all AlGaInN LEDs, where the light output efficiency drops substantially as the current density in the devices increases beyond some 10 A/cm 2 . In typical 1 W-LEDs operate at 35 A/cm 2 (350 mA in 1 mm 2 dies), efficiency may be only half of its maximum value.…”

Section: Introductionmentioning

confidence: 99%

How Do We Lose Excitation in the Green?

Wetzel

Xia

Zhao

et al. 2013

Frontiers in Electronics

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Efficiency droop and green gap are terms that summarize performance limitations in GaInN/GaN high brightness light emitting diodes (LEDs). Here we summarize progress in the development of green LEDs and report on time resolved luminescence data of polar c-plane and non-polar m-plane material. We find that by rigorous reduction of structural defects in homoepitaxy on bulk GaN and V-defect suppression, higher efficiency at longer wavelengths becomes possible. We observe that the presence of donor acceptor pair recombination within the active region correlates with lower device performance. To evaluate the aspects of piezoelectric polarization we compare LED structures grown along polar and non-polar crystallographic axes. In contrast to the polar material we find single exponential luminescence decay and emission wavelengths that remain stable irrespective of the excitation density. Those findings render high prospects for overcoming green gap and droop in non-polar homoepitaxial growth.

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Characterization of GaInN/GaN layers for green emitting laser diodes

Cited by 10 publications

References 20 publications

Wavelength-stable rare earth-free green light-emitting diodes for energy efficiency

Wavelength-stable rare earth-free green light-emitting diodes for energy efficiency

Submicrometre resolved optical characterization of green nanowire-based light emitting diodes

How Do We Lose Excitation in the Green?

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