Fabrication of AlN templates by high-temperature face-to-face annealing for deep UV LEDs

Uesugi, Kenjiro; Miyake, Hideto

doi:10.35848/1347-4065/ac3026

Cited by 19 publications

(16 citation statements)

References 71 publications

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“…During the HT recrystallization process, the high-density dislocations of the sputtered AlN annihilate, the domain boundaries disappear, and the surface transforms into to a step and terrace morphology. 21 Double sputtering and thermal cycle HTA were further proposed, and the TDD of Alpolar AlN film on sapphire was reduced to 2.4 × 10 7 cm −2 , 22 which is the best result reported so far. Room-temperature lasing of AlGaN-based UVB LDs grown on annealed sputtered AlN templates have been demonstrated.…”

Section: ■ Introductionmentioning

confidence: 85%

Unexpected Realization of N-Polar AlN Films on Si-Face 4H–SiC Substrates Using RF Sputtering and High-Temperature Annealing

Zhang

Guo

Cai

et al. 2023

Crystal Growth & Design

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In this study, we demonstrated AlN films with unexpected N-polarity on Si-face 4H−SiC substrates using RF reactive magnetron sputtering and post high-temperature annealing (HTA). It is found that HTA-AlN sputtered with pure nitrogen or mixed gases of nitrogen and trace oxygen exhibits undoubtable N polarity, which appears to contradict the common assumption of Al-polar AlN on Si-face SiC. The interfacial studies of HTA-AlN sputtered with pure N 2 reveal that the naturally oxidized SiC surface induces the formation of Si−O�Al−N bonds rather than conventional Si�N−Al bonds, thereby causing N-polar AlN. Sputtering with the mixed gases results in 5 nm thick complex transition layers at the AlN/SiC interface, including two types of oxygen-participated energy-unstable inversion domain boundaries and multiple polarity inverted AlN layers. Compared to that sputtered with the mixed gases, the N-polar HTA-AlN film sputtered with pure nitrogen presents a smoother surface morphology for the absence of AlON islands and lower threading dislocation density due to closer X-ray rocking curve full widths at half-maximum for (0002) and (101̅ 2) reflections. This work proves a new approach to prepare high-quality N-polar AlN/SiC templates for Al-rich AlGaN-based N-polar optoelectronic and power devices.

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Section: ■ Introductionmentioning

confidence: 85%

Unexpected Realization of N-Polar AlN Films on Si-Face 4H–SiC Substrates Using RF Sputtering and High-Temperature Annealing

Zhang

Guo

Cai

et al. 2023

Crystal Growth & Design

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“…Recently, a new approach to the fabrication of low-dislocation AlN buffer layers was developed, based on high-temperature face-to-face annealing (HT-FFA) [ 45 , 46 ]. The starting point of the technique is the deposition of poly-crystalline AlN on c-plane sapphire substrates by radio-frequency sputtering of either sintered AlN or high-purity Al targets in the N 2 ambience (the choice of the target controls the dominant polarity of the sputtered film [ 46 ]). Then, two wafers prepared by sputtering were placed face-to-face together and annealed at temperatures of 1600–1750 °C for up to 48 h in N 2 environment.…”

Section: Materials Quality and Its Impact On Internal Quantum Efficie...mentioning

confidence: 99%

“…The HT-FFA technique provided AlN templates with TDD as low as 2 × 10 8 cm −2 . Further TDD reduction to 1.5 × 10 8 cm −2 was accomplished by using thermo-cycling during the annealing stage [ 46 ]. The use of double HT-FFA with a second AlN film deposition on the already annealed template followed by a secondary annealing resulted in the reduction of TDD down to 4.3 × 10 7 cm −2 [ 46 ].…”

Section: Materials Quality and Its Impact On Internal Quantum Efficie...mentioning

confidence: 99%

Towards Efficient Electrically-Driven Deep UVC Lasing: Challenges and Opportunities

Nikishin

Bernussi

Karpov³

2022

Nanomaterials

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The major issues confronting the performance of deep-UV (DUV) laser diodes (LDs) are reviewed along with the different approaches aimed at performance improvement. The impact of threading dislocations on the laser threshold current, limitations on heavy n- and p-doping in Al-rich AlGaN alloys, unavoidable electron leakage into the p-layers of (0001) LD structures, implementation of tunnel junctions, and non-uniform hole injection into multiple quantum wells in the active region are discussed. Special attention is paid to the current status of n- and p-type doping and threading dislocation density reduction, both being the factors largely determining the performance of DUV-LDs. It is shown that most of the above problems originate from intrinsic properties of the wide-bandgap AlGaN semiconductors, which emphasizes their fundamental role in the limitation of deep-UV LD performance. Among various remedies, novel promising technological and design approaches, such as high-temperature face-to-face annealing and distributed polarization doping, are discussed. Whenever possible, we provided a comparison between the growth capabilities of MOVPE and MBE techniques to fabricate DUV-LD structures.

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“…Additionally, the previously found AlN growth is low growth temperature for AlN material, and it is not verified as reducing the growth rate by typical desorption as observed in other materials 20 . Meanwhile, Miyake et al reported low dislocation AlN growth by the sputter-anneal method, which method realized high-temperature with the temperature of 1700 °C by separating in AlN deposition and crystallization 21 , 22 . However, this approach cannot be continuously grown in the device structure and requires renewal by eliminating it from the chamber.…”

Section: Introductionmentioning

confidence: 99%

High growth temperature for AlN by jet stream gas flow metalorganic vapor phase epitaxy

Nagamatsu

Miyagawa

Tomita

et al. 2023

Sci Rep

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Deep ultraviolet light-emitting diodes have attracted considerable attention for realizing virus inactivation applications. The UV-LEDs use the AlN underlying layer and the plane sapphire substrate. However, the low growth temperature in AlN underlying layer is grown by limited growth temperature in conventional MOVPE, and high temperature is preferable for AlN growth. Furthermore, the AlN underlying layer has many dislocations owing to the active layer in the device region when the flat sapphire substrate was used with a dislocation value of > 109 cm−2. We showed the high-temperature crystal growth of AlN with a temperature of 1700 °C by high temperature and gas flow velocity MOVPE. The achieved dislocation density was ~ 4 × 108 cm−2. Additionally, this data means the low dislocation densities in the AlN layer with a growth time of only 15 min and a dislocation density of < 1 × 109 cm−2 are obtained. The AlN growth temperature exceeding 1550 °C decreases the growth rate. These results indicate desorption from the surface of the substrate in a hydrogen atmosphere. Furthermore, the characteristic dislocation behavior of AlN in high-temperature growth at 1700 °C was elucidated from TEM images.

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Fabrication of AlN templates by high-temperature face-to-face annealing for deep UV LEDs

Cited by 19 publications

References 71 publications

Unexpected Realization of N-Polar AlN Films on Si-Face 4H–SiC Substrates Using RF Sputtering and High-Temperature Annealing

Unexpected Realization of N-Polar AlN Films on Si-Face 4H–SiC Substrates Using RF Sputtering and High-Temperature Annealing

Towards Efficient Electrically-Driven Deep UVC Lasing: Challenges and Opportunities

High growth temperature for AlN by jet stream gas flow metalorganic vapor phase epitaxy

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