Improved quality of InGaN/GaN multiple quantum wells by a strain relief layer

Niu, Nanhui; Wang, Huaibing; Liu, Jianping; Liu, Naixin; Xing, Yanhui; Han, Jun; Deng, Jun; Guang-di, Shen

doi:10.1016/j.jcrysgro.2005.09.027

Cited by 76 publications

(45 citation statements)

References 13 publications

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“…The use of such a layer is well documented in the literature, and several mechanisms have been proposed to explain the subsequent improvement of LED efficiency. [2][3][4][5][6][7][8][9][10][11] One of the hypotheses is that the InGaN UL favors the injection of free carriers by creating an electron reservoir, which allows for a better carrier capture efficiency by the QWs. [2][3][4][5][6] However, the improvement of the photoluminescence (PL) properties of InGaN/GaN QWs suggests that the InGaN UL acts on the QW radiative efficiency itself.…”

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confidence: 99%

“…8 Likewise, Nanhui et al proposed that the InGaN UL acts as a strain relief layer, lowering the internal piezoelectric-field and thus alleviating the detrimental impact of the quantum confined Stark effect (QCSE). 9 Other studies have shown that the InGaN UL strongly reduces the density of non-radiative recombination centers (NRCs) and that this decrease is mediated by In atoms. 11 Recently, Armstrong et al confirmed by performing deep level optical spectroscopy that the improvement of LEDs is due to a reduction in the deep level density in the QW active region.…”

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confidence: 99%

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Burying non-radiative defects in InGaN underlayer to increase InGaN/GaN quantum well efficiency

Haller

Carlin

Jacopin

et al. 2017

Applied Physics Letters

111

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The insertion of an InGaN underlayer (UL) is known to strongly improve the performance of InGaN/GaN quantum well (QW) based blue light emitting diodes (LEDs). However, the actual physical mechanism responsible for it is still unclear. We thus conduct a systematic study and investigate different hypotheses. To this aim, InGaN/GaN single (S) QWs are grown on sapphire and GaN free-standing substrates with or without InGaN UL. This allows us to conclude that (i) improvement of LED performance is due to a higher internal quantum efficiency of the InGaN/GaN SQW and (ii) reduction of structural defects is not at play. Furthermore, we show that neither the surface morphology nor the strain of the top GaN layer before the growth of the QW is affected by the InGaN UL. Finally, we find that the beneficial effect of the InGaN UL is still present after 100 nm of GaN. This result combined with band structure modelling rules out the hypothesis of higher QW oscillator strength induced by a reduction of the internal electric field due to band bending. In conclusion, we demonstrate that the increase in InGaN/GaN QW efficiency is the consequence of a reduction of non-radiative recombination centers in the QW itself, independent of the dislocation density.

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mentioning

confidence: 99%

mentioning

confidence: 99%

Burying non-radiative defects in InGaN underlayer to increase InGaN/GaN quantum well efficiency

Haller

Carlin

Jacopin

et al. 2017

Applied Physics Letters

111

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“…Takahashi et al 23 reported that the inclusion of low temperature grown GaN and InGaN prelayers beneath InGaN/GaN single QWs resulted in an increased formation probability of "V"-defects, which are believed to create potential barriers around threading dislocations, thereby inhibiting carrier capture by these extended defects. 24 However, this is somewhat contradictory to the results of the investigation of Nanhui et al, 15,16 in which the authors report a reduction in "V"-defect density associated with the inclusion of a prelayer. We have presented initial results 17 on the effect of including an InGaN:Si prelayer before a MQW stack.…”

Section: Introductionmentioning

confidence: 81%

“…As the internal quantum efficiency (IQE) is determined by competition between radiative and non-radiative recombination processes, slower radiative recombination rates can limit the IQE. It has been reported [10][11][12][13][14][15][16][17][18][19] that the inclusion of an InGaN layer prior to the deposition of the 1st QW, a so-called "prelayer," can lead to significant improvements in the IQE of InGaN multiple QW structures and LEDs. Typical prelayer structures consist of 20-30 nm of intentionally Si-doped (In)GaN, which can be either a single layer or a short-period superlattice, positioned a few nanometers beneath the 1st QW.…”

Section: Introductionmentioning

confidence: 99%

“…Typical prelayer structures consist of 20-30 nm of intentionally Si-doped (In)GaN, which can be either a single layer or a short-period superlattice, positioned a few nanometers beneath the 1st QW. The improvements in IQE have been attributed to either increases in the radiative recombination rate 15,16,18,20,21 or decreases in the nonradiative recombination rate. 11,19 Nanhui et al 15,16 reported that the inclusion of an unintentionally doped 20 nm thick In 0.08 Ga 0.92 N layer in an InGaN/GaN multiple QW structure led to an increase in the photoluminescence (PL) intensity at room temperature.…”

Section: Introductionmentioning

confidence: 99%

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A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers

Davies

Hammersley

Massabuau

et al. 2016

Journal of Applied Physics

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In this paper, we report on a detailed spectroscopic study of the optical properties of InGaN/GaN multiple quantum well structures, both with and without a Si-doped InGaN prelayer. In photoluminescence and photoluminescence excitation spectroscopy, a 2nd emission band, occurring at a higher energy, was identified in the spectrum of the multiple quantum well structure containing the InGaN prelayer, originating from the first quantum well in the stack. Band structure calculations revealed that a reduction in the resultant electric field occurred in the quantum well immediately adjacent to the InGaN prelayer, therefore leading to a reduction in the strength of the quantum confined Stark effect in this quantum well. The partial suppression of the quantum confined Stark effect in this quantum well led to a modified (higher) emission energy and increased radiative recombination rate. Therefore, we ascribed the origin of the high energy emission band to recombination from the 1st quantum well in the structure. Study of the temperature dependent recombination dynamics of both samples showed that the decay time measured across the spectrum was strongly influenced by the 1st quantum well in the stack (in the sample containing the prelayer) leading to a shorter average room temperature lifetime in this sample. The room temperature internal quantum efficiency of the prelayer containing sample was found to be higher than the reference sample (36% compared to 25%) which was thus attributed to the faster radiative recombination rate of the 1st quantum well providing a recombination pathway that is more competitive with nonradiative recombination processes.

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Efficiency Enhancement Mechanism of an Underlying Layer in GaInN‐Based Green Light–Emitting Diodes

Han

Ishimoto

Mano

et al. 2019

Physica Status Solidi (a)

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To investigate the mechanism of efficiency enhancement achieved by introducing underlying layers (ULs) in green light–emitting diodes (LEDs), this study compares green GaInN‐based LEDs with an identical epitaxial structure and chip structure comprising different types of ULs, i.e., without an UL or with a GaInN or AlInN UL. To this end, the samples are analyzed with respect to several characteristics, such as their electroluminescence spectra, internal quantum efficiency, recombination coefficients, joint density of states, localized state, and Stokes shift. Based on these analyses and considerations, a mechanism of efficiency enhancement achieved by introducing ULs is proposed, and the degradation mechanisms responsible for the green gap, efficiency droop, and electrical potential drop in green LEDs are also discussed. The results show that the piezoelectric field in the In‐clustering region and the nonradiative recombination center simultaneously play crucial roles in the degradation mechanisms for green LEDs.

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Improved quality of InGaN/GaN multiple quantum wells by a strain relief layer

Cited by 76 publications

References 13 publications

Burying non-radiative defects in InGaN underlayer to increase InGaN/GaN quantum well efficiency

Burying non-radiative defects in InGaN underlayer to increase InGaN/GaN quantum well efficiency

A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers

Efficiency Enhancement Mechanism of an Underlying Layer in GaInN‐Based Green Light–Emitting Diodes

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