AlyGa1−yN quantum dots (QDs) have been grown by molecular beam epitaxy on AlxGa1−xN (0001) using a 2-dimensional–3-dimensional growth mode transition that leads to the formation of QDs. QDs have been grown for Al compositions y varying between 10% and 40%. The influence of the active region design [composition y, QD height, and bandgap difference (ΔEg) between the AlxGa1−xN cladding layer and the AlyGa1−yN QDs] is discussed based on microscopy, continuous wave photoluminescence (PL), and time-resolved PL (TRPL) measurements. In particular, increasing y leads to a shift of the QD emission toward shorter wavelengths, allowing covering a spectral range in the UV from 332 nm (UVA) to 276 nm (UVC) at room temperature (RT). The low-temperature (LT) internal quantum efficiency of the QD ensembles was estimated from TRPL experiments at 8 K and values between 11% and 66% were deduced. The highest internal quantum efficiency (IQE)-LT is found for the QDs with higher Al content y. Then, the PL spectrally integrated intensity ratios between RT and LT were measured to estimate the IQE of the samples at RT. The PL ratio is higher for larger ΔEg, for QDs with y of 0.1 or 0.2, and high PL intensity ratios up to 30% were also measured for QDs with larger y of 0.3 and 0.4. RT IQE values between 5% and 20% are deduced for AlyGa1−yN QDs emitting in the 276–308 nm range.
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28 November 2019
Research Article|
November 25 2019
Internal quantum efficiencies of AlGaN quantum dots grown by molecular beam epitaxy and emitting in the UVA to UVC ranges
J. Brault
;
J. Brault
a)
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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S. Matta
;
S. Matta
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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T.-H. Ngo;
T.-H. Ngo
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
2
CNRS-Université Montpellier 2, L2C, UMR 5221
, 34095 Montpellier, France
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M. Al Khalfioui;
M. Al Khalfioui
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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P. Valvin;
P. Valvin
2
CNRS-Université Montpellier 2, L2C, UMR 5221
, 34095 Montpellier, France
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M. Leroux;
M. Leroux
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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B. Damilano
;
B. Damilano
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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M. Korytov;
M. Korytov
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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V. Brändli;
V. Brändli
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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P. Vennéguès;
P. Vennéguès
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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J. Massies;
J. Massies
1
Université Côte d’Azur, CNRS, CRHEA
, 06560 Valbonne, France
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B. Gil
B. Gil
2
CNRS-Université Montpellier 2, L2C, UMR 5221
, 34095 Montpellier, France
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a)
Electronic mails: Julien.Brault@crhea.cnrs.fr and smatta@riber.fr
b)
Present address: RIBER S.A., 31 rue Casimir Périer, BP 70083, 95873 Bezons Cedex, France.
J. Appl. Phys. 126, 205701 (2019)
Article history
Received:
June 19 2019
Accepted:
November 03 2019
Citation
J. Brault, S. Matta, T.-H. Ngo, M. Al Khalfioui, P. Valvin, M. Leroux, B. Damilano, M. Korytov, V. Brändli, P. Vennéguès, J. Massies, B. Gil; Internal quantum efficiencies of AlGaN quantum dots grown by molecular beam epitaxy and emitting in the UVA to UVC ranges. J. Appl. Phys. 28 November 2019; 126 (20): 205701. https://doi.org/10.1063/1.5115593
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