Curvature-controllable and crack-free AlN/sapphire templates fabricated by sputtering and high-temperature annealing

Hayashi, Yusuke; Tanigawa, Kenji; Uesugi, Kenjiro; Shojiki, Kanako; Miyake, Hideto

doi:10.1016/j.jcrysgro.2019.02.026

Cited by 12 publications

(11 citation statements)

References 20 publications

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“…The green and yellow dotted lines in Figure 10b indicate the calculated wafer curvature on a basis of thermal stress analysis when the sample was cooled down from a T g of 1300 and 1700 °C to a room temperature of 20 °C. [ 42 ] In that calculation, the thickness of the sapphire substrate is set to 430 μm, and the wafer curvature and strain at a T g were simply assumed to be 0 GPa and 0 km −1 , and other parameters are described elsewhere. [ 42 ] When AlN film thickness is thinner than 4 μm, the obtained wafer curvature was close to the calculated line with a T g of 1700 °C.…”

Section: Resultsmentioning

confidence: 99%

“…[ 42 ] In that calculation, the thickness of the sapphire substrate is set to 430 μm, and the wafer curvature and strain at a T g were simply assumed to be 0 GPa and 0 km −1 , and other parameters are described elsewhere. [ 42 ] When AlN film thickness is thinner than 4 μm, the obtained wafer curvature was close to the calculated line with a T g of 1700 °C. Whereas, the obtained wafer curvatures from the samples with thicker AlN films lie on the calculated line with a T g of 1300 °C.…”

Section: Resultsmentioning

confidence: 99%

“…Note that the AlN film on sapphire is normally subjected to a compressive strain during a cooling down, even though the AlN film is relaxed at the T g , due to the thermal expansion coefficient difference between AlN and sapphire. As it has been discussed in the previous study, [ 42 ] FFA Sp‐AlN is fully relaxed at an FFA temperature of 1700 °C. Therefore, when the AlN film grown coherently on FFA Sp‐AlN, the wafer curvature results in the calculated wafer curvature on the basis of thermal stress analysis with a T g of 1700 °C.…”

Section: Resultsmentioning

confidence: 99%

“…Nonetheless, our results imply that there are methods to reduce the wafer curvature of MOVPE‐grown AlN films on FFA Sp‐AlN, such as the use of thin epilayers and/or AlN depositions on both sides of a substrate. [ 42 ]…”

Section: Resultsmentioning

confidence: 99%

See 3 more Smart Citations

High‐Quality AlN Template Prepared by Face‐to‐Face Annealing of Sputtered AlN on Sapphire

Shojiki

Uesugi

Kuboya

et al. 2020

Physica Status Solidi (b)

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This study comprehensively investigates the properties of metalorganic vapor phase epitaxy (MOVPE)‐grown AlN films on high‐quality face‐to‐face annealed sputtered AlN (FFA Sp‐AlN) templates on sapphire substrates, which are highly important to control the surface morphology for various applications, such as UV light‐emitting diodes and laser diodes. The conditions of thermal cleaning and AlN growth by MOVPE are investigated to remove numerous small islands on as‐annealed FFA Sp‐AlN. Subsequent to thermal cleaning in H2 + NH3 at 1300 °C, MOVPE growth is performed with varying NH3 flow rate and growth temperature (Tg) under a constant pressure and group‐III flow rate. An atomically flat surface with an atomic step‐and‐terrace structure is obtained at a growth rate of ≈1.0 μm h−1 and a Tg of 1300 °C. Transmission electron microscopy images and secondary‐ion mass spectrometry reveal low dislocation densities and impurity concentrations. Finally, the effects of compressive strain in FFA Sp‐AlN on the lattice constant and curvature of the MOVPE‐grown AlN film on FFA Sp‐AlN are investigated. The compressive strain of the AlN film, which is carried over from FFA Sp‐AlN, can prevent crack formation but leads to a large wafer curvature after cooling down from the Tg.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

High‐Quality AlN Template Prepared by Face‐to‐Face Annealing of Sputtered AlN on Sapphire

Shojiki

Uesugi

Kuboya

et al. 2020

Physica Status Solidi (b)

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“…The RLP denoted as (q x , q z ) for AlN is (À3.709, 10.037), which is almost consistent with the unstrained bulk AlN of (À3.71, 10.037). [13,14] This means that the AlN layer in this article is almost relaxed. As shown in Figure 1c, the black arrowed line extended from (À3.71, 10.037) of the fully relaxed AlN to (À3.62, 9.642) of the fully relaxed GaN represents the fully relaxed Al x Ga 1-x N. It should be noted that the RLP of fully relaxed GaN is beyond the coordinates.…”

Section: Resultsmentioning

confidence: 99%

High‐Performance AlGaN‐Based Solar‐Blind UV Photodetectors for Sensing Applications

Zheng

Chen

2021

Physica Status Solidi (a)

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The full solid‐state, intrinsic cutoff solar‐blind UV photodetectors are widely used in the military and civilian fields. Herein, to achieve real‐time solar‐blind UV signal detection for application in portable equipment, the material epitaxy, device fabrication, and performance characterization of high‐performance back‐illuminated AlGaN‐based solar‐blind UV photodetectors are conducted at first. Based on the photodetector, a discrete signal amplifier circuit is subsequently designed and prepared to fulfill the weak solar‐blind signal detection. Through assembling the amplifier circuit with the AlGaN‐based solar‐blind UV photodetector, it can output real‐time voltage signal with different amplitude according to the intensity of the incident UV light signal. This study is of great significance for developing a portable solar‐blind UV detection system.

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High‐Temperature Annealing and Patterned AlN/Sapphire Interfaces

Hagedorn

Mogilatenko

Walde

et al. 2021

Physica Status Solidi (b)

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Using the example of epitaxial lateral overgrowth of AlN on trench-patterned AlN/sapphire templates, the impact of introducing a high-temperature annealing step into the process chain is investigated. Covering the open surfaces of sapphire trench sidewalls with a thin layer of AlN is found to be necessary to preserve the trench shape during annealing. Both the influence of annealing temperature and annealing duration are investigated. To avoid the deformation of the AlN/sapphire interface during annealing, the annealing duration or annealing temperature must be low enough. Annealing for 1 h at 1730 C is found to allow for the lowest threading dislocation density of 3.5 Â 10 8 cm À2 in the subsequently grown AlN, while maintaining an uncracked smooth surface over the entire 2 in. wafer. Transmission electron microscopy study confirms the defect reduction by high-temperature annealing and reveals an additional strain relaxation mechanism by accumulation of horizontal dislocation lines at the interface between annealed and nonannealed AlN. By applying a second annealing step, the dislocation density can be further reduced to 2.5 Â 10 8 cm À2 .

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Curvature-controllable and crack-free AlN/sapphire templates fabricated by sputtering and high-temperature annealing

Cited by 12 publications

References 20 publications

High‐Quality AlN Template Prepared by Face‐to‐Face Annealing of Sputtered AlN on Sapphire

High‐Quality AlN Template Prepared by Face‐to‐Face Annealing of Sputtered AlN on Sapphire

High‐Performance AlGaN‐Based Solar‐Blind UV Photodetectors for Sensing Applications

High‐Temperature Annealing and Patterned AlN/Sapphire Interfaces

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