Chemically ordered<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Al</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi mathvariant="normal">Ga</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:mi mathvariant="normal">N</mml:mi></mml:mrow></mml:math>alloys: Spontaneous formation of natural quantum wells

Albrecht, M.; Lymperakis, Liverios; Neugebauer, Jörg; Northrup, John E.; Kirste, Lutz; Leroux, M.; Grzegory, I.; Porowski, S.; Strunk, H. P.

doi:10.1103/physrevb.71.035314

Cited by 56 publications

(72 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, Albrecht et al have measured a ;100 meV shift in the bandgap of a random alloy with respect to a disordered alloy of similar AlN mole fraction. 12 Ordering in AlGaN alloys was first reported by Korakakis et al, who observed the spontaneous formation of 2ML superlattices consisting of alternating AlN and GaN monolayers along the growth direction (0001) when the films were deposited under low III/V flux ratio conditions. 13 The existence of ordering was verified by the observation of the odd reflections (0001), (0003), etc.…”

Section: Resultsmentioning

confidence: 94%

Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

Sampath

Garrett

Collins

et al. 2006

J. Electron. Mater.

View full text Add to dashboard Cite

Interest in developing ultraviolet emitters using the III-Nitride family of semiconductors has sparked considerable effort in fabricating AlGaN alloys that exhibit enhanced luminescence based on strong carrier localization, similar to their InGaN brethren. In this paper, we report on the growth of such alloys by plasma-assisted molecular beam epitaxy (PA-MBE) without the use of indium. This enhancement is attributed to the presence of nanoscale compositional inhomogeneities (NCIs) in these materials. The emission wavelength in these materials has been tuned between 275 nm and 340 nm by varying growth conditions. The effects of dislocations on double heterostructures (DHs) that employ an NCI AlGaN active region has been investigated, with an internal quantum efficiency as high as 32% obtained for the lowest dislocation density samples (3 3 10 10 cm ÿ2 ). Prototype DH-ultraviolet light emitting diodes (DH-UVLEDs) emitting at 324 nm were fabricated employing an NCI AlGaN alloy as the active region.

show abstract

Section: Resultsmentioning

confidence: 94%

Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

Sampath

Garrett

Collins

et al. 2006

J. Electron. Mater.

View full text Add to dashboard Cite

show abstract

“…On the other hand, the similar periodic sequence of Ga-rich ultrathin clusters may occur as the formation of group-III bilayers owing to the different coordination of the group-III atoms at the step edges of the wurtzite AlGaN layers. The complex kinetics of such Gaincorporation has been studied both theoretically [18,19] and experimentally [9,20].…”

Section: Contributedmentioning

confidence: 99%

Exciton recombination in spontaneously formed and artificial quantum wells Al_xGa_1‐xN/Al_yGa_1‐yN (x<y∼0.8)

Торопов

Shevchenko

Shubina

et al. 2016

Phys. Status Solidi C

View full text Add to dashboard Cite

We report on photoluminescence (PL) spectroscopy and electron microscopy studies of an AlGaN quantum well (QW) structure grown by molecular beam epitaxy under metal‐rich conditions with substrate rotation. Both techniques reveal unintentional formation within the AlGaN barriers of a quasiperiodic structure of thin Ga‐rich layers, whose period is controlled by both the substrate rotation rate and the AlGaN growth rate. These compositional modulations act as 1‐3 monolayer thick QWs emitting below 250 nm with an internal quantum efficiency (IQE) as high as ∼30% at room temperature under weak excitation. Variational calculations of the QW exciton properties indicate that the observed high IQE can result from strong three‐dimensional localization of the excitons confined in the narrow QWs. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

show abstract

“…The spontaneous chemical ordering is similar to what was observed in AlGaN 16,17,18 and InGaN films 19 . Theoretically, the ordering in wurtzite Al x Ga 1-x N was suggested to be driven by the different binding energy of Al-N bond and Ga-N bond 20,21 . The adatom surface diffusion generally allows the incorporation of Al and Ga atoms at their different preferential sites, leading to the ordering sequence of Al-rich and Ga rich areas along the growth axis.…”

mentioning

confidence: 99%

Alloy inhomogeneity and carrier localization in AlGaN sections and AlGaN/AlN nanodisks in nanowires with 240–350 nm emission

Himwas

Hertog

Dang

et al. 2014

Applied Physics Letters

View full text Add to dashboard Cite

The Al-Ga intermixing at Al(Ga)N/GaN interfaces in nanowires and the chemical inhomogeneity in Al x Ga 1-x N/AlN nanodisks (NDs) are attributed to the strain relaxation process. This interpretation is supported by the three-dimensional strain distribution calculated by minimizing the elastic energy in the structure. The alloy inhomogeneity increases with Al content, leading to enhanced carrier localization signatures in their optical characteristics i.e. red shift of the emission, s-shaped temperature dependence and linewidth broadening. Despite these alloy fluctuations, the emission energy of AlGaN/AlN NDs can be tuned in the 240-350 nm range with internal quantum efficiencies around 30%.AlGaN/AlN quantum wells (QWs) 1 and quantum dots (QDs) 2,3, 4 have become promising active media for solid-state ultraviolet lighting. Nanodisks (NDs) in nanowires (NWs) have also emerged as alternative nanostructures which offer not only strong carrier localization 5,6 but also a possibility to improve photon extraction efficiency 7 . However, synthesis of ternary alloys in NWs generally suffers from strong chemical inhomogeneities 8 , which modify their electronic properties with respect to random alloys.Here, we present structural and optical studies of AlGaN sections and AlGaN/AlN NDs in NWs. In the case of AlGaN sections, alloy gradient and spontaneous chemical ordering were found along the wire axis, in addition to the formation of an Alrich shell. We found that alloy fluctuations increase in AlGaN sections with higher Al content, as evidenced by stronger carrier localization in their optical characteristics. At GaN/Al(Ga)N interfaces, we identify a transition zone with strong Al-Ga intermixing whose formation is attributed to the strain relaxation process. This interpretation is supported by a three-dimensional (3D) strain simulation. Despite the radial and axial alloy inhomogeneity, the photon emission energy of AlGaN/AlN NDs can be tuned by adjusting the nominal thickness and Al content.AlGaN sections and stacks of AlGaN/AlN NDs on GaN NWs were grown on Si (111) by plasma-assisted molecular beam epitaxy (PAMBE). Initially, a thin (~2 nm) AlN buffer layer 9 was grown at the substrate temperature T s = 840°C. Then, T s was decreased to 795 °C for the growth of GaN NWs using a Ga flux Φ Ga ~ 0.17 ML/s while the flux of active nitrogen was set at Φ N = 0.34 ML/s to maintain N-rich conditions. The deposition time of GaN NWs was t = 2.5 hours. Then, the Al x Ga 1-x N sections or the Al x Ga 1-x N/AlN NDs were synthesized on the top of these GaN NWs. The deposition time of AlGaN sections was 40 min, while that of AlGaN NDs was between 10 and 40 s with ~1 min AlN barriers. To adjust the nominal Al content (x = Φ Al /Φ N ) in the Al x Ga 1-x N, the Al flux was varied in the Φ Al = 0.07-0.17 ML/s range, while keeping Φ Ga = 0.09 ML/s and Φ N = 0.34 ML/s for the entire growth process. The Al, Ga and N deposition rates were calibrated by reflection high-energy electron diffraction intensity oscillations during the growth of two-di...

show abstract

Chemically orderedAlxGa1−xNalloys: Spontaneous formation of natural quantum wells

Cited by 56 publications

References 20 publications

Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

Exciton recombination in spontaneously formed and artificial quantum wells Al_xGa_1‐xN/Al_yGa_1‐yN (x<y∼0.8)

Alloy inhomogeneity and carrier localization in AlGaN sections and AlGaN/AlN nanodisks in nanowires with 240–350 nm emission

Contact Info

Product

Resources

About

Chemically orderedAlxGa1−xNalloys: Spontaneous formation of natural quantum wells

Cited by 56 publications

References 20 publications

Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

Growth of AlGaN alloys exhibiting enhanced luminescence efficiency

Exciton recombination in spontaneously formed and artificial quantum wells AlxGa1‐xN/AlyGa1‐yN (x<y∼0.8)

Alloy inhomogeneity and carrier localization in AlGaN sections and AlGaN/AlN nanodisks in nanowires with 240–350 nm emission

Contact Info

Product

Resources

About

Exciton recombination in spontaneously formed and artificial quantum wells Al_xGa_1‐xN/Al_yGa_1‐yN (x<y∼0.8)