High-Power, Low-Efficiency-Droop Semipolar ($20\bar{2}\bar{1}$) Single-Quantum-Well Blue Light-Emitting Diodes

Pan, Chih-Chien; Tanaka, Shinichi; Wu, Feng; Zhao, Yuji; Speck, James S.; Nakamura, Shuji; DenBaars, Steven P.; Feezell, Daniel

doi:10.1143/apex.5.062103

Cited by 114 publications

(138 citation statements)

References 29 publications

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“…3 for In 0.14 Ga 0.86 N/GaN QWs, the electric field across (11 22) QWs caused by the spontaneous and piezoelectric polarizations in the wells and GaN barriers is roughly estimated to be about 3-times weaker than in polar QWs. The peak shift variation of the PSS-and BulkLEDs is in good agreement with values of $1.3-2.0 nm previously reported for (11 22 33 Thus, these small peak shifts indicate a weak QCSE in semipolar InGaN QWs. Figure 4 shows P opt of the unpackaged PSS-and BulkLEDs measured in DC mode inside an integrating sphere as a function of I inject .…”

Section: Resultssupporting

confidence: 91%

“…45,46 Generally, the much smaller droop of nonpolar and semipolar LEDs in comparison with polar LEDs has been attributed to the weaker polarization fields. [30][31][32][33]47,48 However, it should be noted that low-efficiency polar LEDs also show a relatively small droop, 35,36 which has been attributed mainly to the strong effect of non-radiative recombination processes. Recently, Davies et al 49 have suggested that the droop is inherent to the carrier density in InGaN QW structures and independent of crystal orientation.…”

Section: Resultsmentioning

confidence: 99%

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Role of substrate quality on the performance of semipolar (112¯2) InGaN light-emitting diodes

Dinh

Corbett

Parbrook

et al. 2016

Journal of Applied Physics

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We compare the optical properties and device performance of unpackaged InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) emitting at ∼430 nm grown simultaneously on a high-cost small-size bulk semipolar (112¯2) GaN substrate (Bulk-GaN) and a low-cost large-size (112¯2) GaN template created on patterned (101¯2) r-plane sapphire substrate (PSS-GaN). The Bulk-GaN substrate has the threading dislocation density (TDD) of ∼105 cm−2–106 cm−2 and basal-plane stacking fault (BSF) density of 0 cm−1, while the PSS-GaN substrate has the TDD of ∼2 × 108 cm−2 and BSF density of ∼1 × 103 cm−1. Despite an enhanced light extraction efficiency, the LED grown on PSS-GaN has two-times lower internal quantum efficiency than the LED grown on Bulk-GaN as determined by photoluminescence measurements. The LED grown on PSS-GaN substrate also has about two-times lower output power compared to the LED grown on Bulk-GaN substrate. This lower output power was attributed to the higher TDD and BSF density.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Role of substrate quality on the performance of semipolar (112¯2) InGaN light-emitting diodes

Dinh

Corbett

Parbrook

et al. 2016

Journal of Applied Physics

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“…In fact there are examples of LEDs with a low droop published in the recent literature, in these cases they were typically grown on a low dislocation density bulk GaN substrate. 13,14 If we take the cases where the dislocation density is around or below 10 6 cm À2 , we may assume that the dislocation influence on droop can be neglected, and the residual droop in such cases may be understood to be Fig. 3(b) corresponding to areas with lower and higher dislocation density, respectively.…”

Section: -2mentioning

confidence: 99%

Dislocation related droop in InGaN/GaN light emitting diodes investigated via cathodoluminescence

Pozina

Ciechonski

et al. 2015

Applied Physics Letters

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Todays energy saving solutions for general illumination rely on efficient white light emitting diodes (LEDs). However, the output efficiency droop experienced in InGaN based LEDs with increasing current injection is a serious limitation factor for future development of bright white LEDs. We show using cathodoluminescence (CL) spatial mapping at different electron beam currents that threading dislocations are active as nonradiative recombination centers only at high injection conditions. At low current, the dislocations are inactive in carrier recombination due to local potentials, but these potentials are screened by carriers at higher injection levels. In CL images, this corresponds to the increase of the dark contrast around dislocations with the injection (excitation) density and can be linked with droop related to the threading dislocations. Our data indicate that reduction of droop in the future efficient white LED can be achieved via a drastic reduction of the dislocation density by using, for example, bulk native substrates. (C) 2015 AIP Publishing LLC.

Funding Agencies|Swedish Research Council (VR); Swedish Energy Agency

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“…Also the intrinsic field leads to a spatial separation of electron and hole wave functions, causing a reduced radiative recombination rate [4,6], an effect that can be particularly undesirable for high-efficiency optoelectronic devices. To circumvent these effects arising from the intrinsic built-in fields, which fundamentally are caused by the growth along the polar c axis, significant research has been directed towards the fabrication of semi-and nonpolar structures [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In the case of semi-and nonpolar planes the c axis is at a nonvanishing angle with respect to the growth direction.…”

Section: Introductionmentioning

confidence: 99%

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

Schulz¹,

Tanner

O’Reilly

et al. 2015

Phys. Rev. B

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In this paper we present a detailed analysis of the structural, electronic, and optical properties of an m-plane (In,Ga)N/GaN quantum well structure grown by metal organic vapor phase epitaxy. The sample has been structurally characterized by x-ray diffraction, scanning transmission electron microscopy, and 3D atom probe tomography. The optical properties of the sample have been studied by photoluminescence (PL), time-resolved PL spectroscopy, and polarized PL excitation spectroscopy. The PL spectrum consisted of a very broad PL line with a high degree of optical linear polarization. To understand the optical properties we have performed atomistic tight-binding calculations, and based on our initial atom probe tomography data, the model includes the effects of strain and built-in field variations arising from random alloy fluctuations. Furthermore, we included Coulomb effects in the calculations. Our microscopic theoretical description reveals strong hole wave function localization effects due to random alloy fluctuations, resulting in strong variations in ground state energies and consequently the corresponding transition energies. This is consistent with the experimentally observed broad PL peak. Furthermore, when including Coulomb contributions in the calculations we find strong exciton localization effects which explain the form of the PL decay transients. Additionally, the theoretical results confirm the experimentally observed high degree of optical linear polarization. Overall, the theoretical data are in very good agreement with the experimental findings, highlighting the strong impact of the microscopic alloy structure on the optoelectronic properties of these systems.

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High-Power, Low-Efficiency-Droop Semipolar ($20\bar{2}\bar{1}$) Single-Quantum-Well Blue Light-Emitting Diodes

Cited by 114 publications

References 29 publications

Role of substrate quality on the performance of semipolar (112¯2) InGaN light-emitting diodes

Role of substrate quality on the performance of semipolar (112¯2) InGaN light-emitting diodes

Dislocation related droop in InGaN/GaN light emitting diodes investigated via cathodoluminescence

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

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