Influence of V-pits on the efficiency droop in InGaN/GaN quantum wells

Kim, Jaekyun; Cho, Yong-Hee; Ko, Dong-Su; Li, Xiang-Shu; Won, Jae-Sun; Lee, Eunha; Park, Seoung–Hwan; Kim, Jun-Youn; Kim, Sungjin

doi:10.1364/oe.22.00a857

Cited by 68 publications

(33 citation statements)

References 41 publications

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“…This demonstrated that the threading dislocations in the V-shaped pits act as energy barriers for the lateral transport of charge [27]. In 2014, Kim et al discussed the influence of V-pits and their energy barrier originating from its facets of (1011) planes, and it revealed that higher V-pit energy barrier heights in InGaN QWs more efficiently suppress the non-radiative recombination at TDs, thus enhancing the internal quantum efficiency (IQE) [28]. Chang et al applied superlattice layers to manipulate the nanoscale V-pits and obtain the optimum V-pits size to achieve high-efficiency blue wavelength InGaN/GaN LEDs [22].…”

Section: Introductionmentioning

confidence: 99%

Effects of Nanoscale V-Shaped Pits on GaN-Based Light Emitting Diodes

Chen

2017

Materials

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This paper reviews the formation of nanoscale V-shaped pits on GaN-based light emitting diodes (LEDs) grown by the metal organic chemical vapor deposition (MOCVD) system and studies the effect of V-shaped pits on quantum efficiency. Since V-pits could provide potential barriers around threading dislocations to lessen non-radiative recombinations in such a high defect environment. In our study, multiple InGaN/GaN quantum well samples with different emission wavelengths of 380, 420, 460, and 500 nm were grown, each with different nanoscale V-shaped pits of three diameters for 150, 200, and 250 nm, respectively. It was found that the multiple quantum well (MQW) sample with larger V-pits had a lower pit density, but a relatively larger total V-pits defected area. The optimum diameter of V-pits showing the highest quantum efficiency from the MQW sample depended on the emission wavelength. MQW samples with wavelengths of 380 and 500 nm exhibited the best internal quantum efficiency (IQE) performance at the smallest V-pits area; however, the best performance for MQW samples with wavelength around 420 and 460 nm occurred when large V-pit areas were presented. Photoluminescence (PL) peak shifts and Raman shifts can provide a relationship between quantum-confined Stark effect (QCSE) and IQE, as well as a comparison between strain and IQE. The results obtained in this phenomenological study shall provide a useful guide line in making high-performance GaN-based LEDs with wide emission spectra.

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Section: Introductionmentioning

confidence: 99%

Effects of Nanoscale V-Shaped Pits on GaN-Based Light Emitting Diodes

Chen

2017

Materials

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“…Thus, only a few dark spots and many black points are present in Figure 2d-f. The black points caused by TD may have become nonradiative recombination centers and seriously degraded the LED performance [27]. In short, lower prestrained layers growth temperature led to bigger and more V-pits formed.…”

Section: Monochromatic Analysismentioning

confidence: 99%

“…Studies have reported that V-shaped pits could degrade LED performance by increasing the probability of nonradiative recombination and causing leakage current [12,[23][24][25]. However, some recent studies have revealed that V-shaped pits may be beneficial for InGaN-based LEDs when pit morphology and density are properly controlled [24,26,27]. The optimal V-pit size and opening angle are 200-250 nm and 60 • , respectively, and achieving these parameters can increase light emission efficiency [28][29][30].By contrast, the QCSE caused by interior strain among InGaN/GaN MQWs reduces emission efficiency because of the reduced overlap of wavefunctions between electrons and holes.…”

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confidence: 99%

Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes

Chen

2020

Crystals

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Strains and V-shaped pits are essential factors for determining the efficiency of GaN-based light-emitting diodes (LEDs). In this study, we systematically analyzed GaN LED structures on patterned sapphire substrates (PSSs) with two types of growth temperature employed for prestrained layers and three different thickness of n-type GaN layers by using cathodoluminescence (CL), microphotoluminescence (PL), and depth-resolved confocal Raman spectroscopy. The results indicated that V-pits formation situation can be analyzed using CL. From the emission peak intensity ratio of prestrained layers and multiple quantum wells (MQWs) in the CL spectrum, information regarding strain relaxation between prestrained layers and MQWs was determined. Furthermore, micro-PL and depth-resolved confocal Raman spectroscopy were employed to validate the results obtained from CL measurements. The growth conditions of prestrained layers played a dominant role in the determination of LED performance. The benefit of the thick layer of n-GaN was the strain reduction, which was counteracted by an increase in light absorption in thick n-type doped layers. Consequently, the most satisfactory LED performance was observed in a structure with relatively lower growth temperature of prestrained layers that exhibited larger V-pits, leading to higher strain relaxation and thinner n-type GaN layers, which prevent light absorption caused by n-type GaN layers.

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“…The most challenging issues in InGaN-based nitride semiconductors include the spatial fluctuation of indium composition and the generation of dislocations at the interface of InGaN-based heterostructures due to the limited solubility of indium atom into GaN because of the difference in the In-N and Ga-N bond length [52][53][54]. Because of dislocations the non-radiative recombination increases, leading to the rapid decrease in the performance of the InGaN-based devices [55,56].…”

Section: Polar Ingan/gan Heterostructuresmentioning

confidence: 99%

Heterostructures of III-Nitride Semiconductors for Optical and Electronic Applications

Roul¹,

Chandan²,

Mukundan³

et al. 2018

Epitaxy

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III-Nitride-based heterostructures are well suited for the fabrication of various optoelectronic devices such as light-emitting diodes (LEDs), laser diodes (LDs), high-power/-high-frequency field-effect transistors (FETs), and tandem solar cells because of their inherent properties. However, the heterostructures grown along polar direction are affected by the presence of internal electric field induced by the existence of intrinsic spontaneous and piezoelectric polarizations. The internal electric field is deleterious for optoelectronic devices as it causes a spatial separation of electron and hole wave functions in the quantum wells, which thereby decreases the emission efficiency. The growth of III-nitride heterostructures in nonpolar or semipolar directions is an alternative option to minimize the piezoelectric polarization. The heterostructures grown on these orientations are receiving a lot of focus due to their potential improvement on the efficiency of optoelectronic devices. In the present chapter, the growth of polar and nonpolar III-nitride heterostructures using molecular beam epitaxy (MBE) system and their characterizations are discussed. The transport properties of the III-nitride heterostructure-based Schottky junctions are also included. In addition, their applications toward UV and IR detectors are discussed.

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Influence of V-pits on the efficiency droop in InGaN/GaN quantum wells

Cited by 68 publications

References 41 publications

Effects of Nanoscale V-Shaped Pits on GaN-Based Light Emitting Diodes

Effects of Nanoscale V-Shaped Pits on GaN-Based Light Emitting Diodes

Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes

Heterostructures of III-Nitride Semiconductors for Optical and Electronic Applications

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