Dislocation densities reduction in MBE-grown AlN thin films by high-temperature annealing

Némoz, M.; Dagher, Roy; Matta, Samuel; Michon, A.; Vennéguès, P.; Brault, J.

doi:10.1016/j.jcrysgro.2016.12.089

Cited by 40 publications

(27 citation statements)

References 27 publications

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“…This feature is in agreement with the EL spectra which show large FWHMs up to 60-70 nm at low J. It is the consequence of fluctuations in the QD active regions in terms of QD size (i.e., mainly the QD height since lateral confinement effects in Al y Ga 1−y N QDs are weak compared to those along the <0001> direction due to a height over diameter ratio of the order of 4 [28]) and Al composition including the intrinsic alloy inhomogeneous broadening as discussed in previous works [24,32]. Regarding the EL and the PL intensity modulation, it is influenced by a Fabry-Perot effect resulting from the high refractive index contrasts at the AlGaN/sapphire and the air/AlGaN interfaces.…”

Section: Discussionmentioning

confidence: 70%

“…The Mg concentrations in each layer, based on calibrations by secondary ion mass spectroscopy on reference samples, are estimated to be about 5 × 10 19 atoms•cm −3 in both Al 0.7 Ga 0.3 N and Al 0.8 Ga 0.2 N layers and 1 × 10 20 atoms•cm −3 in the top GaN layer. From the growth processes used to fabricate the LED structures and previous studies that are based on X-ray diffraction and transmission electron microscopy measurements performed on reference samples [32], the TDD in the LED structures is estimated to be ranging between: TDD~6-8 × 10 10 cm −2 for the AlN template and TDD~3-6 × 10 10 cm −2 for the Al 0.7 Ga 0.3 N/Al 0.2 Ga 0.8 N QD structures [31].…”

Section: Methodsmentioning

confidence: 99%

“…In fact, for both structures, the emission ranges from about 280 nm to 400 nm. Yet, the band gap of Al 0.2 Ga 0.8 N is estimated at an energy of 3.89 eV that corresponds to a wavelength of 319 nm [32]. Therefore, the broadening of the PL spectrum is attributed to the QD sizes and/or Al compositions fluctuations [24].…”

Section: Photoluminescencementioning

confidence: 99%

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UVB LEDs Grown by Molecular Beam Epitaxy Using AlGaN Quantum Dots

et al. 2020

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AlGaN based light emitting diodes (LEDs) will play a key role for the development of applications in the ultra-violet (UV). In the UVB region (280–320 nm), phototherapy and plant lighting are among the targeted uses. However, UVB LED performances still need to be improved to reach commercial markets. In particular, the design and the fabrication process of the active region are central elements that affect the LED internal quantum efficiency (IQE). We propose the use of nanometer-sized epitaxial islands (i.e., so called quantum dots (QDs)) to enhance the carrier localization and improve the IQE of molecular beam epitaxy (MBE) grown UVB LEDs using sapphire substrates with thin sub-µm AlN templates. Taking advantage of the epitaxial stress, AlGaN QDs with nanometer-sized (≤10 nm) lateral and vertical dimensions have been grown by MBE. The IQE of the QDs has been deduced from temperature dependent and time resolved photoluminescence measurements. Room temperature IQE values around 5 to 10% have been found in the 290–320 nm range. QD-based UVB LEDs were then fabricated and characterized by electrical and electroluminescence measurements. On-wafer measurements showed optical powers up to 0.25 mW with external quantum efficiency (EQE) values around 0.1% in the 305–320 nm range.

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Section: Discussionmentioning

confidence: 70%

Section: Methodsmentioning

confidence: 99%

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UVB LEDs Grown by Molecular Beam Epitaxy Using AlGaN Quantum Dots

et al. 2020

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“…On the other hand, Al-AlN cermet thin films have been reported for several applications and recently as a solar absorber coating [9,10]. AlN films have been deposited with various methods, such as Chemical Vapor Deposition (CVD) [11], Metal-Organic Chemical Vapor Deposition (MOCVD) [12], Plasma-Source Molecular Beam Epitaxy (PSMBE) [13], reactive sputter deposition [14], molecular beam epitaxy [15] and Pulsed Laser Deposition (PLD) [16,17]. Particularly, PLD is a well suited method for depositing AlN thin films for optical applications since it is able to produce high-quality films at low deposition temperatures.…”

Section: Introductionmentioning

confidence: 99%

Deposit of AlN thin films by nitrogen reactive pulsed laser ablation using an Al target

et al. 2019

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We report the synthesis of AlN hexagonal thin films by pulsed laser ablation, using Al target in nitrogen ambient over natively-oxidized Si (111) at 600°C. Composition and chemical state were determined by X-ray photoelectron spectroscopy (XPS); while structural properties were investigated using X-ray diffraction (XRD). High-resolution XPS spectra present a gradual shift to higher binding energies on the Al2ppeak when nitrogen pressure is incremented, indicating the formation of the AlN compound. At 30 mTorr nitrogen pressure, theAl2p peak corresponds to AlN, located at 73.1 eV, and the XRD pattern shows a hexagonal phase of AlN. The successful formation of the AlN compound is corroborated by UV-Vis reflectivity measurements.

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“…To tackle these questions, we have studied the effect of the exposure of AlN surfaces to a silane flux at temperatures above 1300 °C. In fact, it has been shown that, at these temperatures, atom mobility is sufficiently high to promote a significant improvement of the crystalline quality of AlN layers 13,14 . This mobility may enhance the Al/Si atomic exchanges.…”

Section: Introductionmentioning

confidence: 99%

Al5+αSi5+δN12, a new Nitride compound

Dagher¹,

Lymperakis²,

Delaye³

et al. 2019

Sci Rep

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The family of III-Nitride semiconductors has been under intensive research for almost 30 years and has revolutionized lighting applications at the dawn of the 21st century. However, besides the developments and applications achieved, nitride alloys continue to fuel the quest for novel materials and applications. We report on the synthesis of a new nitride-based compound by using annealing of AlN heteroepitaxial layers under a Si-atmosphere at temperatures between 1350 °C and 1550 °C. The structure and stoichiometry of this compound are investigated by high resolution transmission electron microscopy (TEM) techniques and energy dispersive X-Ray (EDX) spectroscopy. Results are supported by density functional theory (DFT) calculations. The identified structure is a derivative of the parent wurtzite AlN crystal where the anion sublattice is fully occupied by N atoms and the cation sublattice is the stacking of 2 different planes along <0001>: The first one exhibits a ×3 periodicity along <11–20> with 1/3 of the sites being vacant. The rest of the sites in the cation sublattice are occupied by an equal number of Si and Al atoms. Assuming a semiconducting alloy, a range of stoichiometries is proposed, Al5+αSi5+δN12 with α being between −2/3 and 1/4 and δ between 0 and 3/4.

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Dislocation densities reduction in MBE-grown AlN thin films by high-temperature annealing

Cited by 40 publications

References 27 publications

UVB LEDs Grown by Molecular Beam Epitaxy Using AlGaN Quantum Dots

UVB LEDs Grown by Molecular Beam Epitaxy Using AlGaN Quantum Dots

Deposit of AlN thin films by nitrogen reactive pulsed laser ablation using an Al target

Al5+αSi5+δN12, a new Nitride compound

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