Collinear Polarization of Exciton/Biexciton Photoluminescence from Single Hexagonal GaN Quantum Dots

Kindel, Christian; Kako, Satoshi; Kawano, Takeshi; Oishi, H.; Arakawa, Yasuhiko

doi:10.1143/jjap.48.04c116

Cited by 14 publications

(10 citation statements)

References 7 publications

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“…41 along with a sign correction for one of the piezoelectric constants 16. In agreement with the experimentally observed fine structure splitting of the excitonic bright states 10, 29, 34, an additional structural in‐plane elongation of 20% was included in the modeling. Finally, the dipole moment of the excitonic bright states was determined by summing up the Hartree–Fock state densities of the electrons and the holes with appropriate signs.…”

Section: Theory: Excitonic Dipole Momentsmentioning

confidence: 64%

“…3b. Also variations in a volume maintaining QD elongation of up to 20% 10, 29 change the calculated excitonic dipole moment for large towards small QDs by maximal ∼20% down to negligible 0.5%, clearly emphasizing the importance of the QD height. It is also exactly this QD height that tunes the radiative decay time of excitons in wurtzite GaN/AlN QDs over several orders of magnitude 31.…”

Section: Theory: Excitonic Dipole Momentsmentioning

confidence: 95%

“…Generally, luminescence traces of single hexagonal GaN/AlN QDs exhibit remarkably broad emission lines in the meV regime 26. This well‐known feature 7, 14, 27–30 is particularly surprising given the long radiative lifetimes of wurtzite GaN/AlN QDs ranging from the ns to the µs regime 31, 32 pointing to homogeneous emission linewidths down to the µeV range. We show that the apparent emission linewidth discrepancy of over three orders of magnitude is predominantly caused by spectral diffusion, as supported by the observation of a unique scaling behavior between the median emission linewidths and the QDs' emission energies.…”

Section: Introductionmentioning

confidence: 99%

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Spectral diffusion in nitride quantum dots: Emission energy dependent linewidths broadening via giant built‐in dipole moments

Kindel

Callsen

Kako

et al. 2014

Physica Rapid Research Ltrs

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1 Introduction Quantum light sources exhibiting one-and two-photon emission are the key requirement for quantum cryptography ultimately leading to truly secure data transmission [1]. Physical realization can be obtained by parametric down-conversion [2], atomic [3], or defect related transitions [4,5] and quantum dot (QD) luminescence [6,7]. Tailoring the electronic structure of a highly integrable [8] semiconductor QD even leads to tunability of the resulting photon streams [9] based on variation of vital parameters as the exciton fine-structure splitting [10][11][12] and the biexciton binding energy [13][14][15][16].Hence, the precise determination of such parameters is mandatory for the design of quantum light sources, but the emission linewidth broadening due to spectral diffusion can make such task a tough challenge. The general phenomenon of spectral diffusion was first described in nu-

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Section: Theory: Excitonic Dipole Momentsmentioning

confidence: 64%

Section: Theory: Excitonic Dipole Momentsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Spectral diffusion in nitride quantum dots: Emission energy dependent linewidths broadening via giant built‐in dipole moments

Kindel

Callsen

Kako

et al. 2014

Physica Rapid Research Ltrs

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“…1͑a͔͒. 14,15 Biexcitonic emission is observed with negative ͑i.e., antibinding͒ biexciton binding energy in agreement with previous studies. 2,11,16,17 The polarization has been interpreted to stem from valence-band mixing effects induced by shape/strain anisotropy of the QD.…”

mentioning

confidence: 99%

“…2,11,16,17 The polarization has been interpreted to stem from valence-band mixing effects induced by shape/strain anisotropy of the QD. 14,15,18,19 Presence of FIG. 1.…”

mentioning

confidence: 99%

Exciton fine-structure splitting in GaN/AlN quantum dots

et al. 2010

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Exciton bright-state fine-structure splitting ͑FSS͒ in single GaN/AlN quantum dots ͑QDs͒ is reported, presenting an important step toward the realization of room temperature single-qubit emitters for quantum cryptography and communication. The FSS in nitride QDs is up to 7 meV and thus much larger than for other QD systems. We find also a surprising dependence of FSS on the QD size, inverse to that of arsenide QDs. Now we are able to explain why FSS can only be observed in small QDs of high-emission energies. Our calculations reveal a shape/strain anisotropy as origin of the large FSS allowing different approaches to control FSS in nitrides.Zero-dimensional semiconductor nanostructures, such as self-assembled quantum dots ͑QDs͒, are unique to study and exploit features of single, discrete quantum systems for realworld applications, such as devices generating singlepolarized photons ͑qubits͒ or entangled photon pairs on demand. 1-5 Such devices might present the physical basis for future practical quantum cryptography and communication systems. 6-8 Until now electrically driven qubit emitters have been demonstrated at cryogenic temperatures only based on Group III-As QDs. 1,3,9 Ubiquitous room-temperature devices for quantum-information systems on demand must be based on QDs with a much deeper confinement potential such as GaN/AlN QDs. No exciton bright-state fine-structure splitting ͑FSS͒ for such QDs has been reported yet and detailed theoretical understanding of exchange interaction in wurtzites is missing. We present in this Rapid Communication the first comprehensive experimental and theoretical study of FSS in GaN/AlN QDs. Values up to 7 meV are reported, much larger than in other semiconductor QDs. 10-13 Surprisingly, the dependence of FSS on emission energy reported here is inverse to that of arsenide-based QDs. These observations are well explained by our theoretical modeling based on realistic k · p wave functions. We are able to identify the anisotropic strain distribution in the QD as origin of the FSS. Our discoveries open new ways to effectively control the FSS, toward the realization of qubit emitters on demand operating at room temperature.The self-assembled hexagonal GaN/AlN QDs investigated in this work were grown by low-pressure metalorganic vapor deposition on 100 nm AlN on n-type 6H-SiC ͓0001͔ substrate and capped with another 100 nm AlN layer. The samples were processed to mesa structures to facilitate single-dot microphotoluminescence measurements. 2 A frequency-doubled solid-state laser with = 266 nm was used to excite the QDs with varying excitation power at 4 K. Polarization-dependent optical spectra were taken using a / 2 waveplate and a Glan-Taylor polarizer. For an accurate assignment of linear-polarization angle and degree of polarization P we took 36 spectra per QD while rotating the waveplate by ⌬␣ = 5°per spectrum. The integrated peak intensities I were then fitted by I͑␣͒ = I 0 / 2͓1+ P cos͑4␣ −2͔͒.has an accuracy of Ϸ5°. The error of P is estimated as 20% due to the difficulty of...

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Flying qubits and entangled photons

Unrau

Bimberg²

2013

Laser & Photonics Reviews

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Efficient generation of polarized single photons or entangled photon pairs is crucial for the implementation of quantum key distribution (QKD) systems. Self organized semiconductor quantum dots (QDs) are capable of emitting on demand one polarized photon or an entangled photon pair upon current injection. Highly efficient single-photon sources consist of a pin structure inserted into a microcavity where single electrons and holes are funneled into an InAs QD via a submicron AlOx aperture, leading to emission of single polarized photons with record purity of the spectrum and non-classicality of the photons. A new QD site-control technique is based on using the surface strain field of an AlO x current aperture below the QD. GaN/AlN QD based devices are promising to operate at room temperature and reveal a fine-structure splitting (FSS) depending inversely on the QD size. Large GaN/AlN QDs show disappearance of the FSS. Theory also suggests QDs grown on (111)-oriented GaAs substrates as source of entangled photon pairs.

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Collinear Polarization of Exciton/Biexciton Photoluminescence from Single Hexagonal GaN Quantum Dots

Cited by 14 publications

References 7 publications

Spectral diffusion in nitride quantum dots: Emission energy dependent linewidths broadening via giant built‐in dipole moments

Spectral diffusion in nitride quantum dots: Emission energy dependent linewidths broadening via giant built‐in dipole moments

Exciton fine-structure splitting in GaN/AlN quantum dots

Flying qubits and entangled photons

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