Control of the Oscillator Strength of the Exciton in a Single InGaN-GaN Quantum Dot

Jarjour, Anas F.; Oliver, Rachel A.; Tahraoui, A.; Kappers, Menno J.; Humphreys, C. J.; Taylor, Robert A.

doi:10.1103/physrevlett.99.197403

Cited by 59 publications

(66 citation statements)

References 20 publications

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“…The small ND is 15 nm in diameter and should have the least amount of strain. It was found to be QD-like and will be called QD-ND in this paper.The emission from the QW-ND is strongly influenced by the strain in the InGaN layer, common to III-N QWs grown on c-plane 4,17 . At low excitation intensities, as shown in Fig.…”

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confidence: 99%

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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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confidence: 99%

“…The emission from the QW-ND is strongly influenced by the strain in the InGaN layer, common to III-N QWs grown on c-plane 4,17 . At low excitation intensities, as shown in Fig.…”

mentioning

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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“…This allows tuning of the QD emission across a wide range of wavelengths and control of the oscillator strength by application of an external bias 4 . The disadvantage of the internal electric fields, however, is the spatial separation of the electron and hole wavefunctions that reduces the radiative recombination efficiency due to the quantum confined Stark effect (QCSE), and which leads to long exciton lifetimes increasing the time-jitter on the emission from a single photon source and reducing the available repetition rate.…”

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confidence: 99%

Non-polar (11-20) InGaN quantum dots with short exciton lifetimes grown by metal-organic vapor phase epitaxy

Zhu

Oehler

Reid

et al. 2013

Applied Physics Letters

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We report on the optical characterization of non-polar a-plane InGaN quantum dots (QDs) grown by metal-organic vapor phase epitaxy using a short nitrogen anneal treatment at the growth temperature. Spatial and spectral mapping of sub-surface QDs have been achieved by cathodoluminescence at 8 K. Microphotoluminescence studies of the QDs reveal resolution limited sharp peaks with typical linewidth of 1 meV at 4.2 K. Time-resolved photoluminescence studies suggest the excitons in these QDs have a typical lifetime of 538 ps, much shorter than that of the c-plane QDs, which is strong evidence of the significant suppression of the internal electric fields.

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“…With the technological advancement of the crystal growing, not only Q2D nitride QW and Q1D nitride QWR structures, but also quasi-0-dimensional (Q0D) nitride quantum dots (QDs) can be fabricated [17][18][19][20][21][22][23][24][25][26][27]. It is well known that group-III nitride usually crystallizes in the hexagonal wurtzite structure, whose physical behavior is anisotropic in space.…”

Section: Zhangmentioning

confidence: 99%

Polar interface optical phonon states and their dispersive properties of a wurtzite GaN quantum dot: quantum size effect

Zhang¹

2010

Condens. Matter Phys.

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Based on the macroscopic dielectric continuum model, the interface-optical-propagating (IO-PR) mixing phonon modes of a quasi-zero-dimensional (Q0D) wurtzite cylindrical quantum dot (QD) structure are derived and studied. The analytical phonon states of IO-PR mixing modes are given. It is found that there are two types of IO-PR mixing phonon modes, i.e. ρ-IO/z-PR mixing modes and the z-IO/ρ-PR mixing modes existing in Q0D wurtzite QDs. Each IO-PR mixing mode also has symmetrical and antisymmetrical forms. Via a standard procedure of field quantization, the Fröhlich Hamiltonians of electron-(IO-PR) mixing phonons interaction are obtained. The orthogonal relations of polarization eigenvectors for these IO-PR mixing modes are also displayed. Numerical calculations for a wurtzite GaN cylindrical QD are focused on the quantum size effect on the dispersive properties of IO-PR mixing modes. The results reveal that both the radial-direction size and the axial-direction size have great effect on the dispersive frequencies of the IO-PR mixing phonon modes. The limiting features of dispersive curves of these phonon modes are discussed in depth. The phonon modes "reducing" the behavior of wurtzite quantum confined structures have been explicitly observed in the systems. Moreover, the behaviors that the IO-PR mixing phonon modes in wurtzite Q0D QDs reduce to the IO modes and PR modes in wurtzite Q2D QW and Q1D QWR systems are profoundly analyzed both from the viewpoint of physics and mathematics. These results show that the present theories of polar mixing phonon modes in wurtzite cylindrical QDs are consistent with the phonon modes theories in wurtzite QWs and QWR systems. The analytical electron-phonon interaction Hamiltonians obtained here are useful in further analyzing the phonon effect on optoelectronic properties of wurtzite Q0D QD structures.

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Control of the Oscillator Strength of the Exciton in a Single InGaN-GaN Quantum Dot

Cited by 59 publications

References 20 publications

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

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

Non-polar (11-20) InGaN quantum dots with short exciton lifetimes grown by metal-organic vapor phase epitaxy

Polar interface optical phonon states and their dispersive properties of a wurtzite GaN quantum dot: quantum size effect

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