Evidence for Phase-Separated Quantum Dots in Cubic InGaN Layers from Resonant Raman Scattering

Lemos, V.; Silveira, Eduardo; Leite, J. R.; Tabata, A.; Trentin, R.; Scolfaro, L. M. R.; Frey, Terrence; As, D. J.; Schikora, D.; Lischka, K.

doi:10.1103/physrevlett.84.3666

Cited by 101 publications

(68 citation statements)

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“…Work by Kehagias et al [9] has used EDX mapping to show that InGaN nanorods grown on (111)-Si substrates have increasing In composition along the length of nanorods which is due to high In desorption rates at temperatures of 450°C. In segregation has also been reported in quantum well and quantum dot structures [4] and in other alloy systems such as InGaAs [10].…”

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confidence: 97%

“…This spans the visible spectrum and makes InGaN a viable candidate for optoelectronic devices such as LEDs, lasers and photovoltaics [1,2]. Growth of InGaN may be achieved using various growth techniques such as molecular beam epitaxy (MBE) [3,4], pulsed laser deposition [5] and metal-organic chemical vapour deposition [2,6,7]. However due to a lack of adequately lattice matched substrates InGaN films generally have high threading dislocations.…”

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confidence: 99%

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Transmission electron microscopy of indium gallium nitride nanorods grown by molecular beam epitaxy

Webster

Cherns

Новиков

et al. 2014

Phys. Status Solidi C

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This paper demonstrates the growth of InGaN nanorods and lateral growth over nanorod arrays using molecular beam epitaxy. It is shown that nitrogen rich growth conditions result in a nanorod array and that, by changing to metal rich conditions, lateral growth may be enhanced to coalesce the nanorods into a continuous overgrown film. Energy dispersive X‐ray spectroscopy has been used to demonstrate that the nanorods display a core‐shell structure with In‐rich cores and In‐poor edges. Transmission Electron Microscopy has shown that the nanorods are free of dislocations. However, when lateral growth occurs basal plane stacking faults are generated. It is shown that this stacking fault generation leads to a change in structure from hexagonal to cubic. When coalescence has occurred large angle grain boundaries are present. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Transmission electron microscopy of indium gallium nitride nanorods grown by molecular beam epitaxy

Webster

Cherns

Новиков

et al. 2014

Phys. Status Solidi C

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“…1 However, there is strong evidence that an important emission mechanism originates from phase-separated quantum dots ͑QDs͒ formed by spinodal decomposition taking place in the InGaN alloys, the active media in these devices. [2][3][4] Spinodal decomposition occurs below a critical temperature and for a range of the alloy composition which defines a miscibility gap at a given temperature. It has been recognized from theory for a long time that the critical temperature lowers significantly due to biaxial strain in coherently grown semiconductor epitaxial layers and the miscibility gap may even be suppressed.…”

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Phase separation suppression in InGaN epitaxial layers due to biaxial strain

Tabata

Teles

Scolfaro

et al. 2002

Applied Physics Letters

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104

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Phase separation suppression due to external biaxial strain is observed in InxGa1−xN alloy layers by Raman scattering spectroscopy. The effect is taking place in thin epitaxial layers pseudomorphically grown by molecular-beam epitaxy on unstrained GaN(001) buffers. Ab initio calculations carried out for the alloy free energy predict and Raman measurements confirm that biaxial strain suppress the formation of phase-separated In-rich quantum dots in the InxGa1−xN layers. Since quantum dots are effective radiative recombination centers in InGaN, we conclude that strain quenches an important channel of light emission in optoelectronic devices based on pseudobinary group-III nitride semiconductors.

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“…6,[20][21][22][23][24][25] It has been found that the internal quantum efficiency can be enhanced by nanoscale islands or quantum dots observed in AlGaN. 6,20,24 Moreover, atomic-scale compositional superlattice (SL) has also been observed in Al-rich AlGaN thin films grown by molecular-beam epitaxy.…”

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confidence: 99%

Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN)5/(GaN)1 superlattice with MgGa-ON δ-codoping: Role of O-atom in GaN monolayer

et al. 2015

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We calculate Mg-acceptor activation energy EA and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on EA in nanoscale (AlN)5/(GaN)1 superlattice (SL), a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMgGa-ON (n = 1-3) complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing EA. The shorter the Mg-O bond is, the smaller the EA is. The Mg-acceptor activation energy can be reduced significantly by nMgGa-ON δ-codoping. Our calculated EA for 2MgGa-ON is 0.21 eV, and can be further reduced to 0.13 eV for 3MgGa-ON, which results in a high hole concentration in the order of 1020 cm−3 at room temperature in (AlN)5/(GaN)1 SL. Our results prove that nMgGa-ON (n = 2,3) δ-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.

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Evidence for Phase-Separated Quantum Dots in Cubic InGaN Layers from Resonant Raman Scattering

Cited by 101 publications

References 20 publications

Transmission electron microscopy of indium gallium nitride nanorods grown by molecular beam epitaxy

Transmission electron microscopy of indium gallium nitride nanorods grown by molecular beam epitaxy

Phase separation suppression in InGaN epitaxial layers due to biaxial strain

Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN)5/(GaN)1 superlattice with MgGa-ON δ-codoping: Role of O-atom in GaN monolayer

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