Diffusion in GaN/AlN superlattices: DFT and EXAFS study

Aleksandrov, I. A.; Малин, Т. В.; Журавлев, К. С.; Трубина, С. В.; Эренбург, С. Б.; Pécz, B.; Lebiadok, Y. V.

doi:10.1016/j.apsusc.2020.146001

Cited by 25 publications

(11 citation statements)

References 41 publications

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“…Previous calculations of the vacancy defect migration present conflicting conclusions. Our higher basal barrier of Al vacancy migration matches the results from the work of Aleksandrov et al , 101 where by using a first-principles method the barrier for the Al vacancy migration was found to be higher than that for the Ga vacancy migration in GaN. However, Warnick et al 99 found a lower barrier (1.6 eV) for Al vacancy migration in AlGaN alloy than in pure GaN, which agrees with our lower barrier results.…”

Section: Resultssupporting

confidence: 92%

“…After Limpijumnong & Van de Walle's comprehensive theoretical study on intrinsic defect migration in GaN using DFT, several other studies followed. 31,98–102 But there has not been a detailed computational investigation on intrinsic defect migration in AlN, only some comparisons with GaN. 31,101 Here we will present our computational results of a systematic study of defect migration in AlN and compare with currently available data from studies on GaN and InN.…”

Section: Resultsmentioning

confidence: 99%

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Computational study of native defects and defect migration in wurtzite AlN: an atomistic approach

et al. 2023

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Computational study of native defects and defect migration in wurtzite AlN: an atomistic approach

et al. 2023

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“…These values are of the same order of magnitude of 10−10 to 10−14 cm2 s−1 as the Ga-Al interdiffusion coefficients experimentally found in annealed GaN/AlN at a temperature of about 1000°C to 1100°C 25 . Nevertheless, these values are higher than that calculated in a prior reference 26 for diffusion of Ga in GaN via a vacancy mediated mechanism, which reported about 10−26 to 10−17 cm2 s−1 at a temperature range of 850°C to 1300°C. In fact, the theoretical predictions did not take into account the Ga diffusion through dislocations and extended defects emerging from the GaN/GaAs interface.…”

Section: Ga Self-diffusion In Gansupporting

confidence: 68%

Analysis and simulation of the in-situ time-resolved reflectivity recorded during the growth of GaN on GaAs (110) substrate

Othmani,

Daldoul,

Chaaben

et al. 2024

Opt. Eng.

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The growth rate of GaN on the GaAs (110) substrate as deduced from reflectivity measurements exhibits a peculiar behavior. A transient regime with a relatively high initial growth rate progressively decreases to a limit value during the early stage of high temperature GaN growth. An optical model, incorporating time-dependent profiles of the growth rate and surface roughness, was used to simulate the corresponding in situ reflectivity recorded during the growth of GaN layers on the GaAs (110) substrate. The growth rate transient, characterized by a time constant ðτÞ and a diffusion length (L), is proposed to originate from Ga self-diffusion in the GaN layer. Both the time constant ðτÞ and the diffusion length ðLÞ increase with the rising growth temperature. This allows for the estimation of the Ga self-diffusion coefficient in GaN, which, in the growth temperature range of 750°C to 900°C, was found to be equal to D ¼ 1.35 10 −11 expð−ð0.28∓0.04Þ∕k B T Þ cm 2 s −1 .

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“…Moreover, the presence of vacancies in the AlGaN could provide paths for group-III atoms to move to the surface and desorb, [29] which results in even more vacancies in the bulk. Here, Ga desorption is more likely than Al desorption, considering the high bond energy of Al-N. [27,30] Furthermore, Ivan et al found that the diffusion coefficient of Ga atoms is higher than that of Al atoms, both in AlN and GaN. [30] Meanwhile, for x Al = 0.55, the XRD measurements do not indicate a reduction in the TDD after HTA.…”

Section: Resultsmentioning

confidence: 99%

“…Here, Ga desorption is more likely than Al desorption, considering the high bond energy of Al-N. [27,30] Furthermore, Ivan et al found that the diffusion coefficient of Ga atoms is higher than that of Al atoms, both in AlN and GaN. [30] Meanwhile, for x Al = 0.55, the XRD measurements do not indicate a reduction in the TDD after HTA. The Ga desorption during HTA may also result in Al content fluctuation, which is significant for AlGaN with lower x Al .…”

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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Diffusion in GaN/AlN superlattices: DFT and EXAFS study

Cited by 25 publications

References 41 publications

Computational study of native defects and defect migration in wurtzite AlN: an atomistic approach

Computational study of native defects and defect migration in wurtzite AlN: an atomistic approach

Analysis and simulation of the in-situ time-resolved reflectivity recorded during the growth of GaN on GaAs (110) substrate

Role of Oxygen Incorporation in High Temperature Annealed AlGaN

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