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Satake, Akihiro; Masumoto, Yasuaki; Miyajima, Takao; Asatsuma, Tsunenori; Nakamura, Fumihiko; Ikeda, Masao

doi:10.1103/physrevb.57.r2041

Cited by 126 publications

(72 citation statements)

References 15 publications

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“…However, it was recently demonstrated that the reduction of dislocations can improve the lifetime of GaN-based laser diodes [2,3]. To understand this apparent contradiction, it is necessary to know not only the radiative emission mechanism of the GaInN active layer with threading dislocations [4][5][6][7], but also the optical properties of the threading dislocations themselves.…”

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confidence: 99%

Threading Dislocations and Optical Properties of GaN and GaInN

Miyajima¹,

Hino²,

Tomiya

et al. 2001

phys. stat. sol. (b)

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We categorized threading dislocations in GaN and GaInN multiple quantum wells and epitaxially lateral overgrown GaN into three types of line defects (edge, screw and mixed dislocations), and investigated the optical properties. It was confirmed by cathodoluminescence measurements that not only screw and mixed dislocations but also edge dislocations act as non-radiative centers in GaN. Epitaxial lateral overgrowth (ELO) technique can reduce the densities of all line-defects in a several mm wide wing region. Growth steps in the wing region were disturbed by the defects which were left in a seed region, and a complicated structure was formed at the surface of GaN and GaInN layers grown on ELO-GaN at low temperature. We believe that this surface structure formed by high supersaturation is a cause of In compositional spatial fluctuation and phase separation of GaInN alloy.

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mentioning

confidence: 99%

Threading Dislocations and Optical Properties of GaN and GaInN

Miyajima¹,

Hino²,

Tomiya

et al. 2001

phys. stat. sol. (b)

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“…Such behavior of the luminescence band is characteristic for the localized-state filling in disordered systems. 10,11 In contrast, no considerable shifting is observed in the quaternary AlInGaN samples. We attribute the observed changes in the SSEPL to the indium-induced reduction of the band-tail states in the AlGaN sublattice.…”

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confidence: 62%

“…We attribute this shift to the carrier localization effect in the bandtail states of a partially disordered crystal. 10,12 With incorporation of In in quaternary AlInGaN layers, the spectral distribution of the decay time flattens, the peak decay time decreases, and the shift disappears. These TRL features point to a transition from a localized-to delocalized-carrier regime.…”

mentioning

confidence: 99%

Optical bandgap formation in AlInGaN alloys

Тамулайтис

Kazlauskas

Juršėnas

et al. 2000

Applied Physics Letters

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We report on the spectral dynamics of the reflectivity, site-selectively excited photoluminescence, photoluminescence excitation, and time-resolved luminescence in quaternary AlInGaN epitaxial layers grown on GaN templates. The incorporation of a few percents of In into AlGaN causes significant smoothening of the band-bottom potential profile in AlInGaN layers owing to improved crystal quality. An abrupt optical bandgap indicates that a nearly lattice-matched AlInGaN/GaN heterostructure with large energy band offsets can be grown for high-efficiency light-emitting devices.

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“…Firstly, it has been postulated [1] that there exist localized states whose energies extend into the band gap of the InGaN QW with a density that decreases exponentially away from the band edges. In this band tail model it can be shown that the decay time increases towards lower transition energies, but the model offers no explanation for the strong dependence on well width of the decay time.…”

Section: Introductionmentioning

confidence: 99%

Effects of Indium Segregation and Well-Width Fluctuations on Optical Properties of InGaN/GaN Quantum Wells

Vala

Godfrey

Dawson

2001

phys. stat. sol. (b)

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We report the results of calculations for the energies of confined electrons and holes and their wavefunction overlap in In x Ga 1--x N/GaN quantum wells (QWs) with an indium concentration of x = 15% in the well material. It is known that the observed increase in the photoluminescence lifetime with increasing well width can be explained qualitatively by the reduction in overlap of the electron and hole wave functions, which is caused by the piezoelectric field in the strained QW material. We show that the energy dependence of the lifetime measured across the emission line can be explained in a similar way, as the result of AE1-monolayer variations in the QW width. We also calculate the energies and electron-hole wave-function overlap for carriers trapped within indium-rich regions of the QW, taking into account the relaxation of the strain field in and around the indium fluctuation. Our results indicate that well-width fluctuations lead to a stronger energy dependence of the lifetime: the magnitude of the effect is the same order as in experiment, and shows a similar increase with increasing well width. IntroductionThe measured photon energy of the photoluminescence (PL) from InGaN quantum wells (QWs) shows a consistent red-shift, compared with the band gap of bulk InGaN alloy material of the same composition. In addition, the PL decay time depends on the photon energy, increasing as the energy of the emission is scanned from the high to the low energy side of the emission line.Various models have been put forward in partial explanation of these results. Firstly, it has been postulated [1] that there exist localized states whose energies extend into the band gap of the InGaN QW with a density that decreases exponentially away from the band edges. In this band tail model it can be shown that the decay time increases towards lower transition energies, but the model offers no explanation for the strong dependence on well width of the decay time. Moreover, if the timescale of the PL decay is to be explained by the relatively slow relaxation of carriers through these localized states, then, by a similar argument, the onset of the PL should be expected to be delayed on a similar timescale. No such effect on the rise time is observed.A second model proposed does not require the existence of localized states, but instead relies on the quantum confined Stark effect (QCSE) in the InGaN wells [2]. Strong spontaneous and piezoelectric polarization effects [3] are expected, the latter arising from the large difference between the in-plane lattice parameters of InN and GaN. The electron and hole wave functions are confined near the edges of the QW and this accounts for both the large downward shifts in emission energy (compared with the

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Localized exciton and its stimulated emission in surface mode from single-layerInxGa1−xN

Cited by 126 publications

References 15 publications

Threading Dislocations and Optical Properties of GaN and GaInN

Threading Dislocations and Optical Properties of GaN and GaInN

Optical bandgap formation in AlInGaN alloys

Effects of Indium Segregation and Well-Width Fluctuations on Optical Properties of InGaN/GaN Quantum Wells

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