Stacking fault-associated polarized surface-emitted photoluminescence from zincblende InGaN/GaN quantum wells

Church, Stephen; Ding, Boning; Mitchell, P.W.; Kappers, Menno J.; Frentrup, Martin; Kusch, Gunnar; Fairclough, Simon M.; Wallis, D. J.; Oliver, Rachel A.; Binks, David J.

doi:10.1063/5.0012131

Cited by 9 publications

(9 citation statements)

References 32 publications

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“…This may be achieved by utilizing QWs grown along alternate crystal directions or in alternate phases that have lower recombination lifetimes, τ, since N = j τ/ et QW , where t QW is the QW thickness. For instance, QWs produced from m -plane wurtzite or zincblende GaN have sub-nanosecond recombination lifetimes rather than lifetimes of 10s or 100s of nanoseconds as typically found for c -plane wurtzite green-emitting QWs . However, no significant reduction in droop has yet been observed in nonpolar QWs , and droop measurements in zincblende GaN QWs have yet to be reported.…”

Section: Discussionmentioning

confidence: 99%

Disentangling the Impact of Point Defect Density and Carrier Localization-Enhanced Auger Recombination on Efficiency Droop in (In,Ga)N/GaN Quantum Wells

et al. 2023

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The internal quantum efficiency of (In,Ga)N/GaN quantum wells can surpass 90% for blue-emitting structures at moderate drive current densities but decreases significantly for longer emission wavelengths and at higher excitation rates. This latter effect is known as efficiency "droop" and limits the brightness of light-emitting diodes (LEDs) based on such quantum wells. Several mechanisms have been proposed to explain efficiency droop including Auger recombination, both intrinsic and defectassisted, carrier escape, and the saturation of localized states. However, it remains unclear which of these mechanisms is most important because it has proven difficult to reconcile theoretical calculations of droop with measurements. Here, we first present experimental photoluminescence measurements extending over three orders of magnitude of excitation for three samples grown at different temperatures that indicate that droop behavior is not dependent on the point defect density in the quantum wells studied. Second, we use an atomistic tight-binding electronic structure model to calculate localization-enhanced radiative and Auger rates and show that both the corresponding carrier density-dependent internal quantum efficiency and the carrier density decay dynamics are in excellent agreement with our experimental measurements. Moreover, we show that point defect density, Auger recombination, and the effect of the polarization field on recombination rates only limit the peak internal quantum efficiency to about 70% in the resonantly excited green-emitting quantum wells studied. This suggests that factors external to the quantum wells, such as carrier injection efficiency and homogeneity, contribute appreciably to the significantly lower peak external quantum efficiency of green LEDs.

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Section: Discussionmentioning

confidence: 99%

Disentangling the Impact of Point Defect Density and Carrier Localization-Enhanced Auger Recombination on Efficiency Droop in (In,Ga)N/GaN Quantum Wells

et al. 2023

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“…In both cases the valance band offset was assumed to be 20 %. The InGaN bandgaps in the QW and Qwire were calculated using Vergard's Law with a bowing parameter of 1.4 4 ; the In content in the Qwire was taken as being 2.3 times greater than in the QW, due to the In segregation effect reported previously 1,2 . Similarly, the effective masses for both electrons and holes in the QW and Qwire were calculated from the values for GaN and InN using Vergard's Law.…”

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confidence: 99%

Photoluminescence efficiency of zincblende InGaN/GaN quantum wells

Church

Quinn

Cooley-Greene

et al. 2021

Journal of Applied Physics

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Growing green and amber emitting InGaN/GaN quantum wells in the zincblende, rather than the wurtzite, crystal phase has the potential to improve efficiency. However, optimization of the emission efficiency of these heterostructures is still required to compete with more conventional alternatives. Photoluminescence time decays were used to assess how the quantum well width and number of quantum wells affect the recombination rates, and temperature dependent photoluminescence was used to determine the factors affecting recombination efficiency. The radiative recombination lifetime was found to be approximately 600 ps and to increase weakly with well width, consistent with a change in the exciton binding energy. The relative efficiency at room temperature was found to increase by a factor of five when the number of wells was increased from one to five. Furthermore, the efficiency increased by factor 2.2 when the width was increased from 2.5 to 7.5 nm. These results indicate that thermionic emission is the most important process reducing efficiency at temperatures in excess of 100 K. Moreover, the weak dependence of the rate of radiative recombination on well width means that increasing well thickness is an effective way of suppressing thermionic emission and thereby increasing efficiency in zincblende InGaN/GaN quantum wells, in contrast to those grown in the wurtzite phase.

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“…31 The emission spectrum from zb-QWs has been proposed to consist of two components which partially overlap: the QW emission peak and a lower energy peak from the QWires that form in the well. 22 It was thus initially hypothesised that the reduction of the relative intensity of the low energy side was due to saturation of the QWires; however, as described below, polarisation-resolved PL measurements show no evidence for the saturation of QWires within the QW layer. Although it should be noted that the saturation of some other lower energy emitting microstructure within the QW layer could also cause an effective blue shift of the QW emission.…”

Section: Resultsmentioning

confidence: 99%

“…18 In recent years, InGaN/GaN QWs grown in the zincblende (zb) phase have arisen as a promising alternative to the wz structure. Zb-QWs are free of the internal electric fields found in c-plane wz-QWs when grown along the (001) direction 21 and exhibit sub-nanosecond radiative recombination lifetimes, 22 two orders of magnitude lower than those typically found for c-plane QWs. 23 However, the microstructure of zb-QWs can be significantly different from that of their polar and non-polar wz analogues.…”

Section: Introductionmentioning

confidence: 92%