Origin of the “green gap”: Increasing nonradiative recombination in indium‐rich GaInN/GaN quantum well structures

Langer, Torsten; Kruse, Andreas; Ketzer, Fedor Alexej; Schwiegel, Alexander; Hoffmann, Lars; Jönen, H.; Bremers, Heiko; Rossów, U.; Hangleiter, A.

doi:10.1002/pssc.201001051

Cited by 104 publications

(64 citation statements)

References 7 publications

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“…For the 700°C InGaN growth, no emission was identified on the rough a-plane, possibly due to surface states introduced by roughening, acting as paths for nonradiative recombination 41 at high indium concentrations. 42 There were areas with emission peaks from the f10-10g facets at 2.35 eV, 2.62 eV, and a weak emission at 2.95 eV. This is probably caused by a varying indium fraction incorporation on the more irregular surfaces of this sample, while the 2.95 eV may originate from the first-grown region of the InGaN layer observable in the TEM image [see Fig.…”

Section: Characterization Of Indium Gallium Nitride Layersmentioning

confidence: 90%

Investigation of indium gallium nitride facet-dependent nonpolar growth rates and composition for core–shell light-emitting diodes

et al. 2016

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Abstract. Core-shell indium gallium nitride (InGaN)/gallium nitride (GaN) structures are attractive as light emitters due to the large nonpolar surface of rod-like cores with their longitudinal axis aligned along the c-direction. These facets do not suffer from the quantum-confined Stark effect that limits the thickness of quantum wells and efficiency in conventional light-emitting devices. Understanding InGaN growth on these submicron three-dimensional structures is important to optimize optoelectronic device performance. In this work, the influence of reactor parameters was determined and compared. GaN nanorods (NRs) with both f11-20g a-plane and f10-10g m-plane nonpolar facets were prepared to investigate the impact of metalorganic vapor phase epitaxy reactor parameters on the characteristics of a thick (38 to 85 nm) overgrown InGaN shell. The morphology and optical emission properties of the InGaN layers were investigated by scanning electron microscopy, transmission electron microscopy, and cathodoluminescence hyperspectral imaging. The study reveals that reactor pressure has an important impact on the InN mole fraction on the f10-10g m-plane facets, even at a reduced growth rate. The sample grown at 750°C and 100 mbar had an InN mole fraction of 25% on the f10-10g facets of the NRs. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Characterization Of Indium Gallium Nitride Layersmentioning

confidence: 90%

Investigation of indium gallium nitride facet-dependent nonpolar growth rates and composition for core–shell light-emitting diodes

et al. 2016

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“…67 and 68, while the A coefficient was assumed to be roughly proportional to N disl 69 (see also the recent studies on the impact of TDD on LED efficiency presented in Refs. 63,[70][71][72][73][74][75][76]. Auger coefficients were not forced to be the same in LDD and HDD LEDs because, although nominally identical, secondary ion mass spectrometry (SIMS) measures suggest that the QWs of the LDD devices have probably a smoother profile, which could imply a lower Auger rate.…”

Section: D Simulation Studymentioning

confidence: 99%

Correlating electroluminescence characterization and physics-based models of InGaN/GaN LEDs: Pitfalls and open issues

et al. 2014

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Electroluminescence (EL) characterization of InGaN/GaN light-emitting diodes (LEDs), coupled with numerical device models of different sophistication, is routinely adopted not only to establish correlations between device efficiency and structural features, but also to make inferences about the loss mechanisms responsible for LED efficiency droop at high driving currents. The limits of this investigative approach are discussed here in a case study based on a comprehensive set of currentand temperature-dependent EL data from blue LEDs with low and high densities of threading dislocations (TDs). First, the effects limiting the applicability of simpler (closed-form and/or one-dimensional) classes of models are addressed, like lateral current crowding, vertical carrier distribution nonuniformity, and interband transition broadening. Then, the major sources of uncertainty affecting state-of-the-art numerical device simulation are reviewed and discussed, including (i) the approximations in the transport description through the multi-quantum-well active region, (ii) the alternative valence band parametrizations proposed to calculate the spontaneous emission rate, (iii) the difficulties in defining the Auger coefficients due to inadequacies in the microscopic quantum well description and the possible presence of extra, non-Auger high-current-density recombination mechanisms and/or Auger-induced leakage. In the case of the present LED structures, the application of three-dimensional numerical-simulation-based analysis to the EL data leads to an explanation of efficiency droop in terms of TD-related and Auger-like nonradiative losses, with a C coefficient in the 10−30 cm6/s range at room temperature, close to the larger theoretical calculations reported so far. However, a study of the combined effects of structural and model uncertainties suggests that the C values thus determined could be overestimated by about an order of magnitude. This preliminary attempt at uncertainty quantification confirms, beyond the present case, the need for an improved description of carrier transport and microscopic radiative and nonradiative recombination mechanisms in device-level LED numerical models

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“…If the non-radiative recombination pathways are similar then it can be anticipated that the efficiency of green light emission would be less than that of blue emission. However, it has been reported 8,9 that this change in the radiative recombination lifetime is not sufficient to fully explain the reduction in efficiency. It has been suggested that there is also a reduction in the non-radiative recombination lifetime.…”

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confidence: 98%

Effects of quantum well growth temperature on the recombination efficiency of InGaN/GaN multiple quantum wells that emit in the green and blue spectral regions

Hammersley

Kappers

Massabuau

et al. 2015

Applied Physics Letters

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InGaN-based light emitting diodes and multiple quantum wells designed to emit in the green spectral region exhibit, in general, lower internal quantum efficiencies than their blue-emitting counter parts, a phenomenon referred to as the “green gap.” One of the main differences between green-emitting and blue-emitting samples is that the quantum well growth temperature is lower for structures designed to emit at longer wavelengths, in order to reduce the effects of In desorption. In this paper, we report on the impact of the quantum well growth temperature on the optical properties of InGaN/GaN multiple quantum wells designed to emit at 460 nm and 530 nm. It was found that for both sets of samples increasing the temperature at which the InGaN quantum well was grown, while maintaining the same indium composition, led to an increase in the internal quantum efficiency measured at 300 K. These increases in internal quantum efficiency are shown to be due reductions in the non-radiative recombination rate which we attribute to reductions in point defect incorporation.

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Origin of the “green gap”: Increasing nonradiative recombination in indium‐rich GaInN/GaN quantum well structures

Cited by 104 publications

References 7 publications

Investigation of indium gallium nitride facet-dependent nonpolar growth rates and composition for core–shell light-emitting diodes

Investigation of indium gallium nitride facet-dependent nonpolar growth rates and composition for core–shell light-emitting diodes

Correlating electroluminescence characterization and physics-based models of InGaN/GaN LEDs: Pitfalls and open issues

Effects of quantum well growth temperature on the recombination efficiency of InGaN/GaN multiple quantum wells that emit in the green and blue spectral regions

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