High Quality AlN Single Crystal Substrates for AlGaN-Based Devices

Dalmau, Rafael; Craft, H. S.; Britt, J.; Paisley, Elizabeth A.; Moody, Baxter; Guo, Jianqiu; Ji, Yeon Jae; Raghothamachar, Balaji; Dudley, Michael; Schlesser, R.

doi:10.4028/www.scientific.net/msf.924.923

Cited by 27 publications

(32 citation statements)

References 12 publications

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“…AlN single-crystal wafers with a useable area of 85% through process optimization. Later, Dalmau et al 16 obtained a 47 mm high-quality singlecrystal boule by homoepitaxial seeded growth in 2018, and Wang et al 17 AlN-based deep-UV light emitting diodes (DUV-LEDs) have attracted much attention and are expected to replace mercury-vapor lamps for sterilization, water purification, and biochemical sensors. However, the transparency issue of AlN substrates has been considered one of the key obstacles to fabricating high-external quantum efficiency DUV-LEDs.…”

Section: Introductionmentioning

confidence: 99%

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Lei²,

et al. 2022

Crystal Growth & Design

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Crack-free and parasitic-free Al-polar aluminum nitride (AlN) single crystals up to Φ56 mm were iteratively grown by the homoepitaxial physical vapor transport method. The detailed iterative growth processes from the spontaneous AlN boules to Φ56 mm single crystals were presented. Our growth experiments revealed that stable growth of large Al-polar crystals with good structural quality and UV transparency was possible using a pure tungsten setup. For each iteration, the initial expansion angle, which was dominated by the radial temperature gradient (ΔT r ), reached 50−60°under our specific growth system and growth conditions and then gradually decreased to 10−20°during the growth process. For all as-grown crystals, mirror-like facets with a step-flow growth mode could be observed. However, the {101̅ 0} side planes were strongly suppressed when using larger AlN seeds. Material characterization showed that the full width at half maximum of symmetric and asymmetric highresolution X-ray diffraction rocking curves was 84−144 arcsec and 45−70 arcsec, respectively. The average etch pit density evaluated by preferential chemical etching was approximately 8.5 × 10 4 cm −2 . The optical transmission spectra revealed that the entire wafer exhibited excellent ultraviolet (UV) transparency, with absorption coefficients of 19−29 cm −1 in the UV range of 4.43−4.77 eV (260−280 nm).

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Section: Introductionmentioning

confidence: 99%

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Lei²,

et al. 2022

Crystal Growth & Design

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“…Suitable AlN bulk crystals are typically grown by physical vapor transport (PVT). [5][6][7] Optical and electrical properties of the material are determined by intrinsic defects, such as aluminum and nitrogen vacancies (V Al , [8][9][10][11][12][13][14] V N 15,16 ), and extrinsic defects from unintentional background doping by silicon, oxygen, and carbon. These three impurities provide not only isolated substitutional defects (i.e., oxygen and carbon substituting nitrogen, and silicon substituting aluminum: O N, C N, Si Al ), [17][18][19][20][21][22] but are also assumed to form complexes, such as V Al -nSi Al , 23 V Al -nO N (n=1…4 is a number of Si or O atoms), 13,14,16,[23][24][25][26][27][28] C N -Si Al , 29 carbon pairs, 30 and tri-carbon complexes.…”

Section: Introductionmentioning

confidence: 99%

Photochromism and influence of point defect charge states on optical absorption in aluminum nitride (AlN)

Gamov

Hartmann

Straubinger

et al. 2021

Journal of Applied Physics

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In this work, we study the absorption properties of AlN in the range of 1.5 -5.5 eV, as well as the meta-stable change in absorption induced by ultraviolet (UV) irradiation (photochromism), and the restoration of the initial state under the action of irradiation of 2 -4 eV or elevated temperatures. UV irradiation results in a decrease of the absorption coefficient from 110 cm -1 to 55 cm -1 at 4.7 eV while in the visible range the absorption coefficient increases from values below 5 cm -1 to ~35 cm -1 . Measurements with two linear polarizations, E∥c and E⊥c, provide determination of several different absorption bands at 2. 6, 2.8, 3.4, 4.0, 4.5, and 4.8 eV. The bands at 2.6 eV and 3.4 eV identify the defect levels near to the valence band, while the band peaking at 2.8 eV is related to the conduction band. The photochromism allows controlling the absorption of light in two related spectral ranges because the decrease of UV absorption and increase of the visible absorption are related to switching the charge state of the same defects.

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“…However, it is difficult to produce bulk AlN single crystals using melt solidification processes, such as the Czochralski method used for mass production of silicon, because AlN has a high dissociation pressure at high temperatures. Physical vapor transport (PVT) method, [4][5][6][7] hydride vapor phase epitaxy (HVPE) method, [8][9][10] and thermal nitridation of Al 2 O 3 11 have been developed for AlN production. In the case of PVT method, growth of helical crystal has also been developed.…”

Section: Introductionmentioning

confidence: 99%

In‐situ observation of AlN formation from Ni‐Al solution using an electromagnetic levitation technique

et al. 2020

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Aluminum nitride is a promising substrate material for AlGaN-based UV-LED. In order to develop a robust growth processing route for AlN single crystals, fundamental studies of solution growth experiments using Ni-Al alloy melts as a new solution system were performed. Al can be stably kept in solution the Ni-Al liquid even at high temperature; in addition, the driving force of the AlN formation reaction from solution can be controlled by solution composition and temperature. To investigate AlN crystal growth behavior we developed an in situ observation system using an electromagnetic levitation technique. AlN formation behavior, including nucleation and growth, was quantitatively analyzed by an image processing pipeline. The nucleation rate of AlN decreased with increasing growth temperature and decreasing aluminum composition. In addition, hexagonal c-axis oriented AlN crystal successfully grew on the levitated Ni-40 mol%Al droplet reacted at low driving force (1960 K), on the other hand, AlN crystal with dendritic morphology appeared on the sample with higher driving force (Ni-50 mol%Al, 1960 K). Thus, the nucleation rate and crystal morphology were dominated by the driving force of the AlN formation reaction. K E Y W O R D S aluminum nitride, crystal growth, nucleation, thermodynamicsThis is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. How to cite this article: Adachi M, Hamaya S, Yamagata Y, et al. In-situ observation of AlN formation from Ni-Al solution using an electromagnetic levitation technique. J Am Ceram Soc.

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High Quality AlN Single Crystal Substrates for AlGaN-Based Devices

Cited by 27 publications

References 12 publications

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Toward Φ56 mm Al-Polar AlN Single Crystals Grown by the Homoepitaxial PVT Method

Photochromism and influence of point defect charge states on optical absorption in aluminum nitride (AlN)

In‐situ observation of AlN formation from Ni‐Al solution using an electromagnetic levitation technique

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