Role of oxygen diffusion in the dislocation reduction of epitaxial AlN on sapphire during high-temperature annealing

Cancellara, Leonardo; Markurt, Toni; Schulz, Tobias; Albrecht, M.; Hagedorn, Sylvia; Walde, Sebastian; Weyers, M.; Washiyama, Shun; Collazo, Ramón; Sitar, Zlatko

doi:10.1063/5.0065935

Cited by 12 publications

(12 citation statements)

References 24 publications

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“…The origin is oxygen diffusion from the Al 2 O 3 substrate during HT annealing. [ 24,25 ] This feature is not only visible for HTA AlN but also observed for above bandgap excitation of low‐[C], high‐[O] PVT‐grown AlN on tungsten substrates. [ 11 ] Thus, it seems to be a general feature of high‐[O] AlN.…”

Section: Resultsmentioning

confidence: 93%

“…Additionally, the abundance of oxygen in HTA AlN leads to a favored incorporation of O N instead of V N due to lower formation energy, which allows us to separate between the implanted carbon and V N that may form as a compensating donor during a process that involves enough thermal energy to be seen close to thermodynamic equilibrium and lacks the supply of oxygen. [ 23,24 ]…”

Section: Introductionmentioning

confidence: 99%

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A Combination of Ion Implantation and High‐Temperature Annealing: Donor–Acceptor Pairs in Carbon‐Implanted AlN

Peters

Spende

Wolter

et al. 2023

Physica Status Solidi (a)

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Herein, carbon‐implanted high‐temperature annealed (HTA) AlN layers are analyzed and donor–acceptor pair (DAP) transitions probably between the two most abundant impurities, carbon and oxygen, are identified. Both are regarded as the main, hard‐to‐avoid impurities in crystal growth. Oxygen is believed to lead to absorption in the deep UV below a wavelength of 250 nm. In contrast, carbon is the most likely candidate to be responsible for a distinct absorption band around 265 nm. This interpretation has recently been challenged. In this study, carbon‐implanted and HTA AlN layers with ion fluences above 8.1 × 1015 cm−2 are analyzed using low‐temperature and time‐resolved cathodoluminescence spectroscopy. Due to the high concentration of oxygen inside the AlN, as a result of the HTA process, a DAP transition between a most likely carbon‐related acceptor and ON is observed. The measured temperature‐ and power‐dependent blueshift of the peak emission energy as well as the luminescence transients can be clearly explained by a continuous change from a DAP transition at low temperature to a free electron to acceptor transition with increasing temperature. The findings are supported by a configurational coordinate model that describes the measured behavior qualitatively.

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Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

A Combination of Ion Implantation and High‐Temperature Annealing: Donor–Acceptor Pairs in Carbon‐Implanted AlN

Peters

Spende

Wolter

et al. 2023

Physica Status Solidi (a)

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“…Based on ref. [31], this oxygen could create more vacancies in the AlGaN, which enhances the dislocation climb and eventually dislocation reduction by mutual annihilation. The strain relaxation of the AlGaN layers was determined by XRD RSM measurements.…”

Section: Resultsmentioning

confidence: 99%

Role of Oxygen Incorporation in High Temperature Annealed AlGaN

Zainal

Hagedorn

Netzel

et al. 2023

Physica Status Solidi (a)

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Aluminum gallium nitride (AlGaN) based ultraviolet light emitting diodes (UV LEDs) have a variety of applications in areas of biological sensing/detection, optical data communication, medical treatments, and sterilization. However, it is challenging to increase the efficiency of UV LEDs emitting in the UVB and UVC spectral range. [1] One of the approaches to achieve this goal is to develop AlGaN-based UV LEDs on low threading dislocation density (TDD) AlGaN layers.For UV LEDs, AlGaN layers with an Al mole fraction x Al above 0.5 are required to avoid absorption of the UV light generated in the active region of the LEDs. [2][3][4][5] However, it is challenging to reduce the TDD in AlGaN layers. Without improvements in the growth and fabrication process, relaxed or partially relaxed AlGaN layers with x Al > 0.5 usually exhibit a TDD of more than mid-10 9 cm À2 . [6] This is associated with the lattice mismatch between AlGaN and AlN that becomes larger with increasing Ga content. Moreover, relaxation of the AlGaN when growing the layers above the Matthews-Blakeslee critical thickness can lead to surface roughening [7] and generation of new dislocations. [8] Low dislocation density AlGaN layers with the absence of relaxation can be obtained by pseudomorphic growth of the layers on bulk AlN substrates. Nonetheless, pseudomorphic growth is limited by x Al and layer thickness as reported by. [8] For example, pseudomorphic growth of n-Al 0.6 Ga 0.4 N can be achieved with a thickness of up to 0.5 μm, while for n-Al 0.7 Ga 0.3 N, the thickness is up to 1.0 μm. Dalmau et al. found that a 0.4 μm thick Al 0.65 Ga 0.35 N layer already shows 8% of relaxation. [9] In a recent work, [10] pseudomorphic growth was demonstrated for thicker Al 0.6 Ga 0.4 N layers with thicknesses between 0.95 and 3.5 μm. However, these layers suffered from high compressive stress of 3-4 GPa, which could lead to detrimental relaxation in subsequently grown layers with higher Ga content (x Al < 0.6) and huge wafer bow. The latter results in non-uniform growth of the active region of devices and problems in the LED chip process. In the same report, [10] the authors attempted to relieve the stress in the layers by introducing two types of buffer layers, that is, with continuously graded composition and stepwise changed composition, neither of which was successful. From this result, a large barrier for the nucleation of misfit dislocation segments in Al-rich AlGaN layers was concluded. Hence, AlGaN strain relaxation on AlN is challenging especially when growing on low dislocation density AlN buffer layers.At present, UV-transparent bulk AlN substrates are expensive and their availability is still limited. Therefore, AlGaN layers are widely grown on AlN/sapphire templates. A thick fully strained Al 0.8 Ga 0.2 N layer with a TDD of %5 Â 10 8 cm À2 was obtained by growing the layer on maskless epitaxial lateral overgrowth (ELO) AlN/sapphire template. [6,11] In contrast, the TDD was higher

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“…In addition, fast diffusion through dislocation cores has been reported as a diffusion route for oxygen. 47 Thus, oxygen could sufficiently diffuse from the sapphire substrate to form γ -AlON during MOVPE growth.…”

Section: Resultsmentioning

confidence: 99%

Micro- and Nanostructure Analysis of Vapor-Phase-Grown AlN on Face-to-Face Annealed Sputtered AlN/Nanopatterned Sapphire Substrate Templates

Nakanishi

Hayashi

Hamachi

et al. 2023

J. Electron. Mater.

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Micro- and nanostructures in vapor-phase-grown AlN on face-to-face annealed sputtered AlN (FFA Sp-AlN) templates formed on nanopatterned sapphire substrates (NPSS) were comprehensively analyzed using transmission electron microscopy. The comparison between metal–organic vapor-phase epitaxy-grown AlN/FFA Sp-AlN/hole-type NPSS (Sample MOH) and hydride vapor-phase epitaxy-grown AlN/FFA Sp-AlN/cone-type NPSS (Sample HVC) showed apparent differences in the morphology of dislocation propagation, presence of voids, shape of polarity inversion boundaries, and crystal structure on the slope region of NPSS. Notably, cross-sectional and plan-view observations revealed that the quality of FFA Sp-AlN significantly affects the threading dislocation density in the vapor-phase-grown layer. At the slope region of the AlN/NPSS interface, γ -AlON was observed in the MOH sample, while highly misaligned AlN grains were observed in the HVC sample. These characteristic crystal structures affect the occurrence of dislocations via different mechanisms in each sample. This study provides practical information for strategically controlling the micro- and nanostructures formed in AlN/NPSS structures for high-performance AlGaN-based deep-ultraviolet emitters. Supplementary Information The online version contains supplementary material available at 10.1007/s11664-023-10348-3.

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Role of oxygen diffusion in the dislocation reduction of epitaxial AlN on sapphire during high-temperature annealing

Cited by 12 publications

References 24 publications

A Combination of Ion Implantation and High‐Temperature Annealing: Donor–Acceptor Pairs in Carbon‐Implanted AlN

A Combination of Ion Implantation and High‐Temperature Annealing: Donor–Acceptor Pairs in Carbon‐Implanted AlN

Role of Oxygen Incorporation in High Temperature Annealed AlGaN

Micro- and Nanostructure Analysis of Vapor-Phase-Grown AlN on Face-to-Face Annealed Sputtered AlN/Nanopatterned Sapphire Substrate Templates

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