Three-dimensional atom probe analysis of green- and blue-emitting InxGa1−xN∕GaN multiple quantum well structures

Galtrey, M. J.; Oliver, Rachel A.; Kappers, Menno J.; Humphreys, C. J.; Clifton, P. H.; Larson, D.J.; Saxey, David W.; Cerezo, A.

doi:10.1063/1.2938081

Cited by 91 publications

(75 citation statements)

References 18 publications

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“…Our results reveal that the experimentally estimated localization length is consistent with the hole wave function localization, since the localization length of the electrons will be mainly determined by the size of in-plane WWFs, at least for the here considered 25% InN system. It should also be noted that we have studied here the lower limit (5 nm) of the experimentally reported values (5-10 nm) [49]. Thus one could expect that when increasing the in-plane dimension of the WWFs, the localization length of the electrons is of the order 5-10 nm.…”

Section: Comparison With Experimental Datamentioning

confidence: 93%

“…To realize different microscopic configurations, our calculations have been repeated ten times with changing the atomic distribution. Furthermore, experimental studies reveal WWFs at the upper QW interface [49,52]. The diameter of these well-width fluctuations is ≈5-10 nm, while their height is between one and two monolayers.…”

Section: Model Systemmentioning

confidence: 99%

“…Following the experimental data in Refs. [46][47][48][49][50][51], we treat InGaN as a random alloy. To realize different microscopic configurations, our calculations have been repeated ten times with changing the atomic distribution.…”

Section: Model Systemmentioning

confidence: 99%

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Atomistic analysis of the impact of alloy and well-width fluctuations on the electronic and optical properties of InGaN/GaN quantum wells

Schulz¹,

et al. 2015

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We present an atomistic description of the electronic and optical properties of In0.25Ga0.75N/GaN quantum wells. Our analysis accounts for fluctuations of well width, local alloy composition, strain and built-in field fluctuations as well as Coulomb effects. We find a strong hole and much weaker electron wave function localization in InGaN random alloy quantum wells. The presented calculations show that while the electron states are mainly localized by well-width fluctuations, the holes states are already localized by random alloy fluctuations. These localization effects affect significantly the quantum well optical properties, leading to strong inhomogeneous broadening of the lowest interband transition energy. Our results are compared with experimental literature data.

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Section: Comparison With Experimental Datamentioning

confidence: 93%

Section: Model Systemmentioning

confidence: 99%

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Atomistic analysis of the impact of alloy and well-width fluctuations on the electronic and optical properties of InGaN/GaN quantum wells

Schulz¹,

et al. 2015

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“…A range of localisation mechanisms has been proposed including indium clusters, 20,[43][44][45][46] QW width fluctuations, 38,47 and random fluctuations in the local In fraction. 48,49 Of these possibilities, the case for In clusters was largely disproved in the work of Smeeton et al 50 and Galtrey et al, 51 who showed that the evidence for In clustering could be attributed to electron beam damage in the TEM measurements.…”

Section: Polar Quantum Wellsmentioning

confidence: 97%

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

Dawson

Schulz²,

Oliver

et al. 2016

Journal of Applied Physics

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In this paper, we compare and contrast the experimental data and the theoretical predictions of the low temperature optical properties of polar and nonpolar InGaN/GaN quantum well structures. In both types of structure, the optical properties at low temperatures are governed by the effects of carrier localisation. In polar structures, the effect of the in-built electric field leads to electrons being mainly localised at well width fluctuations, whereas holes are localised at regions within the quantum wells, where the random In distribution leads to local minima in potential energy. This leads to a system of independently localised electrons and holes. In nonpolar quantum wells, the nature of the hole localisation is essentially the same as the polar case but the electrons are now coulombically bound to the holes forming localised excitons. These localisation mechanisms are compatible with the large photoluminescence linewidths of the polar and nonpolar quantum wells as well as the different time scales and form of the radiative recombination decay curves.

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“…As analyzed before, 9 the bright regions are on the order of micrometers in size, and have smaller bandgap energy than the dark regions, due to local higher indium concentration 10 or larger quantum well thickness. 11 So carriers are localized in small bandgap energy bright regions.…”

Section: Ecs Journal Of Solid State Science and Technology 4 (2) R10mentioning

confidence: 99%

Optical Characterization of Carrier Localization, Carrier Transportation and Carrier Recombination in Blue-Emitting InGaN/GaN MQWs

Stokes

Armour

2014

ECS J. Solid State Sci. Technol.

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Carrier localization, transportation and recombination in blue-emitting InGaN/GaN multiple quantum wells were analyzed using temperature-dependent photoluminescence spectroscopy, confocal laser scanning microscopy and time-resolved photoluminescence (TRPL). The temperature-dependent shift of PL intensity was fitted with Arrhenius equation and explained using two non-radiative channels, which are related with thermal activation of carriers from different confining potentials. The S-shaped shift of PL peak energy and inverse-S-shaped shift of PL full width at half maximum were explained with carrier localization and carrier transportation. The TRPL spectra taken at several different places from bright region to dark region in the confocal microscopic image showed that the fast decay life-time τ 1 increases with decreasing PL intensity, indicating a higher carrier transportation rate at bright region, while the slow decay life-time τ 2 decreases with decreasing PL intensity, indicating a higher probability of non-radiative recombination at dark region. 2 Previous research has been focused on studying the carrier localization effect in potential minimum using transmission electron microscopy, 3 nearfield scanning optical microscopy. 4 However, not too much work has been focused on the carrier transportation between different regions in the QW layer. In the present work, temperature-dependent photoluminescence (PL), confocal laser scanning microscopy (CLSM) and time-resolved photoluminescence (TRPL) are utilized to analyze the carrier localization and transportation behavior. ExperimentalTwo InGaN/GaN MQWs samples were grown on c-plane sapphire substrate in a Veeco K465i GaN metal-organic chemical vapor deposition (MOCVD) reactor. Triethylgallium (TEGa) and trimethylindium (TMIn) were used as group III sources. Ammonia (NH 3 ) was used as group V source. Nitrogen was used as carrier gas. A 30-nm-thick GaN nucleation layer was grown first on the substrate, followed by a 0.5-μm-thick GaN buffer layer and a 2-μm-thick Si-doped n-type GaN layer. This preliminary structure serves as a GaN template for further growth. Analysis of the GaN template is as follow. The X-ray diffraction (XRD) ω(002) and ω(102) rocking curves scan indicated a TD density of approximately 4.4 × 10 8 cm −2 . The atomic force microscopy (AFM) surface morphology scan of the GaN template in a 5 × 5 μm 2 area exhibited a root mean square (RMS) roughness of 0.4 nm. Four-period MQWs were then grown on the GaN template, consisting of 2.7-nm-thick InGaN quantum well layers and 12.5 nm-thick GaN barrier layers, as was confirmed by XRD. Detailed growth conditions are described elsewhere. 5 The growth temperature was also tuned to achieve a target PL peak wavelength of ∼449 nm, corresponding to an indium composition of ∼14%. Figure 1 shows the system diagram of low-temperature PL system. A Verdi-G10-semiconductor-laser pumped laser system, generating 400 nm CW laser beam, was used as excitation source. The laser beam, after transmitting through an optical fib...

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Three-dimensional atom probe analysis of green- and blue-emitting InxGa1−xN∕GaN multiple quantum well structures

Cited by 91 publications

References 18 publications

Atomistic analysis of the impact of alloy and well-width fluctuations on the electronic and optical properties of InGaN/GaN quantum wells

Atomistic analysis of the impact of alloy and well-width fluctuations on the electronic and optical properties of InGaN/GaN quantum wells

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

Optical Characterization of Carrier Localization, Carrier Transportation and Carrier Recombination in Blue-Emitting InGaN/GaN MQWs

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