Biexciton and exciton dynamics in single InGaN quantum dots

Rice, James H.; Robinson, James W.; Na, Jong H.; Lee, Kwan H.; Taylor, Robert A.; Williams, David P.; O’Reilly, Eoin P.; Andreev, A. D.; Arakawa, Yasuhiko; Yasin, Shazia

doi:10.1088/0957-4484/16/9/010

Cited by 26 publications

(26 citation statements)

References 18 publications

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“…According to reported models of the biexcitonexciton system, the decay curve of the single exciton can be quantitatively described by rate equations. 16,17 In our case, the measured time-dependent I XA does not match well with the modeled decay curve, implying that the assumption of X B being a biexciton is false. 14 Finally, due to the sequential recombination of the biexciton-exciton system, an additive rather than a competitive emission intensity dependence is expected.…”

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confidence: 57%

The charged exciton in an InGaN quantum dot on a GaN pyramid

Hsu

Moskalenko

Eriksson

et al. 2013

Applied Physics Letters

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The emission of a charged exciton in an InGaN quantum dot (QD) on top of a GaN pyramid is identified experimentally. The intensity of the charged exciton exhibits the expected competition with that of the single exciton, as observed in temperature-dependent micro-photoluminescence measurements, performed with different excitation energies. The non-zero charge state of this complex is further supported by time resolved micro-photoluminescence measurements, which excludes neutral alternatives of biexciton. The potential fluctuations in the vicinity of the QD that localizes the charge carriers are proposed to be responsible for the unequal supply of electrons and holes into the QD.

Funding Agencies|NANO-N consortium||Swedish Foundation for Strategic Research (SSF)||

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confidence: 57%

The charged exciton in an InGaN quantum dot on a GaN pyramid

Hsu

Moskalenko

Eriksson

et al. 2013

Applied Physics Letters

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Funding Agencies|NANO-N consortium||Swedish Foundation for Strategic Research (SSF)||

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“…Hence we assign peak X to the single exciton emission, and peak XX to the biexciton-to-exciton transition. 22,23 The large negative binding energies of XX (> 10 meV) are commonly observed in III-N QDs [24][25][26][27][28][29][30][31] . It is due to the residual strain, even in dots with such small sizes, which enhances the repulsive excitonexciton Coulomb interaction 26 .…”

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confidence: 99%

How much better are InGaN/GaN nanodisks than quantum wells—Oscillator strength enhancement and changes in optical properties

Zhang

Lee

Teng

et al. 2014

Applied Physics Letters

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We show over 100-fold enhancement of the exciton oscillator strength as the diameter of an InGaN nanodisk in a GaN nanopillar is reduced from a few micrometers to less than 40 nm, corresponding to the quantum dot limit. The enhancement results from significant strain relaxation in nanodisks less than 100 nm in diameter. Meanwhile, the radiative decay rate is only improved by 10 folds due to strong reduction of the local density of photon states in small nanodisks. Further increase in the radiative decay rate can be achieved by engineering the local density of photon states, such as adding a dielectric coating.InGaN/GaN quantum wells (QWs), with a bandgap tunable over the full visible spectral range, play a vital role in high efficiency visible light emitting diodes (LEDs) and laser diodes 1 . InGaN/GaN quantum dots (QDs) also hold the promise as high temperature quantum photonic devices 2,3 . Unfortunately, a large, strain-induced electric field in III-N heterostructures often severely suppresses the oscillator strength of the exciton and, hence, the radiative decay rate and the internal quantum efficiency (IQE). Since strain is relaxed near free surfaces, nanodisks (NDs) in nanowires, which has a large surfaceto-volume ratio, have been widely considered as a promising solution for improving the IQE of InGaN/GaN photonic devices [4][5][6][7][8][9][10][11] . The accompanying improvement in the radiative decay rate is also important for realizing ultrafast singlephoton sources using InGaN/GaN QDs 3,12 .Despite the observation of enhancements in photoluminescence (PL) intensity and decay rate in InGaN/GaN NDs 4,10,13 , the size-dependent behavior of IQE η int and radiative decay rate γ r , mostly affected by the emitter's oscillator strength f os , remains unclear. Experimental studies using top-down nanopillars reported up to ten-fold enhancement in emission intensity only in nanopillars larger than 100 nm in diameter 10 . However, theoretical studies predicted that strain relaxation is most significant only in the region < 20 nm from the sidewall, suggesting significant improvement of IQE could be possible in small disks ∼ 40 nm in size 9 . Furthermore, no comparisons so far have taken into account the influence of external optical efficiencies on the measured PL intensity, such as input laser absorption efficiency η abs , local density of photon states (LDPS) ρ 14,15 and emission collection efficiency η col 16 , which hinders the extraction of η int , γ r as well as f os .In this work, we systematically compare the PL properties of NDs with diameters ranging from 15 nm to 2 µm. We first present two NDs at the two ends of the diameter range, highlighting their fundamentally different spectral responses to the excitation-induced carrier-screening of piezoelectric fields. We then examine how PL energy, decay time and intensity changes continuously with ND diameter reduction, from which we extract the enhancement of f os , γ r , and η int through careful analysis of various external optical efficiencies.The sample w...

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“…20 To date, merely a few studies compare the exciton and the biexciton dynamics of a single InGaN QD, with the lifetime of the biexciton found to be either approximately the same as that of the exciton 12,21 or significantly longer than that of the exciton. 22 In order to study the recombination lifetimes of both the exciton and the biexciton belonging to the same QD, a reliable spectral identification is required. The expected linear and quadratic excitation power dependences of the photoluminescence (PL) intensities of the exciton and the biexciton, 23 respectively, are not sufficient to guarantee that the emissions originate from the same QD.…”

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confidence: 99%