Size-dependent radiative decay time of excitons in GaN/AlN self-assembled quantum dots

Kako, Satoshi; Miyamura, Miharu; Tachibana, Koji; Hoshino, K.; Arakawa, Yasuhiko

doi:10.1063/1.1596382

Cited by 83 publications

(81 citation statements)

References 18 publications

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“…The existence of the WL peaks, which is a unique feature of QDs grown by SK mode, is consistent with the results of STEM and TEM measurements. The shoulder around 3.05eV comes from the defect states of AlN and SiC [16].…”

Section: Methodsmentioning

confidence: 97%

Stranski–Krastanow growth of stacked GaN quantum dots with intense photoluminescence

Hoshino

Kako

Arakawa

2003

Physica Status Solidi (b)

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PACS 78.55.Cr, 81.15.Gh Multiple-layer stacked GaN quantum dots (QDs) with intense photoluminescence (PL) have been grown by the Stranski-Krastanow growth mode in metalorganic chemical vapor deposition. Scanning transmission electron microscopy (STEM) analysis shows that the vertical aligned QDs are formed, which results from a strain field induced by buried islands. We have also investigated PL spectra at room temperature. The PL intensity increases with increasing number of the stacked layer. This indicates that the carriers can be injected into each layer of GaN quantum dots. , a reduced threshold current density, and a reduced total threshold current [2,3]. In nitride semiconductors, the use of QDs is more effective, since the zero-dimensional electric states in the QDs play an essential role for improving threshold current characteristics particularly in wide bandgap semiconductors [4,5].In order to realize the lasing operation, vertical stacking of the QDs is an important method to increase the total QD density. Stacked QDs have been investigated in various material systems such as InAs/GaAs [6][7][8]. In GaN-based system, lasing oscillation was demonstrated from stacked InGaN QDs grown by metalorganic chemical vapor deposition (MOCVD) under optical excitation [9]. Also, stacked GaN/AlN QDs grwon by molecular beam epitaxy (MBE) were demonstrated by taking advantage of the Stranski-Krastanow (SK) growth mode [10,11].In this paper, we report the growth and optical properties of stacked GaN self-assembled QD structures with the SK growth mode by low-pressure MOCVD. Transmission electron microscopy (TEM) and scanning TEM (STEM) analyses show that existence of the two-dimensional GaN wetting layer (WL) and the vertical self-alignment of the GaN QDs along the growth direction. These results clearly demonstrate formation of QDs with SK mode mainly by the 2.5% lattice mismatch of the GaN/AlN system. We have also investigated photoluminescence (PL) spectra at room temperature. The PL intensity increases with increasing number of stacked layers. This indicates that the carriers can be injected into each layer of GaN quantum dots.

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Section: Methodsmentioning

confidence: 97%

Stranski–Krastanow growth of stacked GaN quantum dots with intense photoluminescence

Hoshino

Kako

Arakawa

2003

Physica Status Solidi (b)

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“…As the height of the QD reduces and the oscillator strength increases [21], the radiative lifetime decreases significantly, increasing the internal quantum efficiency. Shortening the emission wavelength even deeper below 230 nm by utilizing GaN QDs embedded in AlN barriers will further enable applications in sensing and toxic gas detection applications.…”

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confidence: 99%

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

Islam

Protasenko

Lee

et al. 2017

Applied Physics Letters

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The ruggedness, portability, high-efficiency, and microfabrication benefits of solid-state semiconductor light sources over conventional lamps became clear in the last decade for visible wavelengths in the solid-state lighting revolution, and gave birth to several new applications. A similar revolution is expected in the deep-UV spectrum. Semiconductor light sources such as Light-Emitting Diodes (LEDs) and Lasers in the deep ultraviolet (UV) spectrum have versatile applications in water and air purification, in healthcare applications of biophotonic diagnostics and sterilization, in food preservation, in security and environmental monitoring and in industrial curing. The semiconductor material substrate of choice for deep-UV photonic devices is direct-bandgap AlN with an energy bandgap of ~6.2 eV (200 nm), and the active regions where photons are produced are various ternary compositional alloys of AlN with GaN of bandgap ~3.4 eV (365 nm).For deep-UV LEDs, quantum well active regions composed of AlGaN have been used to push the interband optical transition to high energies [1][2][3][4][5]. The internal quantum efficiency in high Al containing AlGaN Quantum Wells (QWs)/barrier structures is limited by the quantum confined stark effect (QCSE) [6][7][8], edge emission due to valence band structure re-ordering [9][10][11], combined with material defect (e.g. dislocation) induced non-radiative recombination. Compositional fluctuations of Al and Ga concentrations in ternary AlGaN alloy layers degrade efficient optical emission in the deep-UV range [12], and together with the other effects degrade the LED efficiency.Distinct from the alloy AlGaN layers, deep-UV emission down to 224 nm has been achieved in binary GaN/AlN heterostructures [13][14][15][16][17]. As a significant advantage, the polarization of the emitted photons in ultrathin GaN QWs and quantum dots/disks (QDs) is perpendicular to the c axis, making them propagate parallel to the c-axis [9,11]; this surface emission property is highly favorable for light extraction.We recently demonstrated deep UV LEDs [18-20] emitting as short as 232 nm by incorporating 2 monolayer (ML) thick GaN QDs in AlN barriers. As the height of the QD reduces and the oscillator strength increases [21], the radiative lifetime decreases significantly, increasing the internal quantum efficiency. Shortening the emission wavelength even deeper below 230 nm by utilizing GaN QDs embedded in AlN barriers will further enable applications in sensing and toxic gas detection applications. Tunable sub-230 nm deep-UV emission was demonstrated by Molecular Beam Epitaxy (MBE) growth of 2 ML GaN QDs using a modified Stranski-Krastanov (m-SK) growth method [22]. The m-SK technique uses thermal annealing of the 2 ML GaN quantum well structure sandwiched between AlN barriers. In this letter, we present an alternative approach to realize tunable sub-230 nm emission with higher internal quantum efficiency using SK growth of 2 ML GaN QD structures by MBE. Unlike the earlier work based on m-SK method, cont...

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“…The reported decay times range between more than 1 µs, for relatively large dots [11], and a few nanoseconds, for smaller ones [8,11]. In this paper we compare continuous-wave PL (CW-PL) results for various excitation densities and time resolved PL (TR-PL) for samples embedding planes of GaN/AlN QDs.…”

Section: Introductionmentioning

confidence: 96%

Nontrivial carrier recombination dynamics and optical properties of over‐excited GaN/AlN quantum dots

Kalliakos

Bretagnon

Lefèbvre

et al. 2004

Physica Status Solidi (b)

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International audienceWe analyze the low temperature photoluminescence properties of two multi-layer stacking of GaN/AlN quantum dots. We report drastic differences of linewidths between continuous wave and time-resolved photoluminescence experiments. After the pulsed excitation, time-resolved photoluminescence reveals a substantial red shift of the line, which keeps a fairly constant width. In continuous wave experiments, the screening of internal electric fields by accumulation of e-h pairs in quantum dot planes induces a blue-shift. For samples with large number of quantum dot planes an unexpected narrowing of the emission line is observed when the laser intensity is increased. We assign the observed behaviors of energies and linewidths to the contributions of the in-depth decrease of the degree of excitation of the different planes. Our interpretation is supported by the use of a model based on a self-consistent solution of the Schrodinger and Poisson equations within the envelope function approximation

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Size-dependent radiative decay time of excitons in GaN/AlN self-assembled quantum dots

Cited by 83 publications

References 18 publications

Stranski–Krastanow growth of stacked GaN quantum dots with intense photoluminescence

Stranski–Krastanow growth of stacked GaN quantum dots with intense photoluminescence

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

Nontrivial carrier recombination dynamics and optical properties of over‐excited GaN/AlN quantum dots

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