Relaxation and recovery processes of AlxGa1−xN grown on AlN underlying layer

Asai, Toshiaki; Nagata, Kouji; Mori, Toshiaki; Nagamatsu, Kentaro; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu

doi:10.1016/j.jcrysgro.2009.01.028

Cited by 15 publications

(14 citation statements)

References 11 publications

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“…2(b) that the SL causes the inclination and annihilation of dislocations but generation of new dislocations in the upper Al 0.2 Ga 0.8 N layer also takes place. We assume that this can be due to the relaxation process of this layer since the critical thickness for Al 0.2 Ga 0.8 N is less than that for Al 0.4 Ga 0.6 N. These results are also in accordance with the data by Asai [18]. The dislocation densities in the upper AlGaN layers estimated by plane-view TEM are 6Â 10 9 cm À 2 and 1 Â 10 10 cm À 2 for samples A and B, respectively.…”

Section: Metal-polar Structures (Samples a B)supporting

confidence: 90%

TEM study of defects in AlxGa1−xN layers with different polarity

Тихонов

Малин

Журавлев

et al. 2012

Journal of Crystal Growth

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Section: Metal-polar Structures (Samples a B)supporting

confidence: 90%

TEM study of defects in AlxGa1−xN layers with different polarity

Тихонов

Малин

Журавлев

et al. 2012

Journal of Crystal Growth

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“…Our results were consistent with Ref. [15]. And the misfit dislocations in the high Al-composition HEMT were considered to be lower than those in the low Al-composition HEMT.…”

supporting

confidence: 93%

“…As discussed in Ref. [15], the degree of relaxation in AlGaN layers on AlN layer is decreased with increasing the Al composition of the AlGaN layer. Our results were consistent with Ref.…”

mentioning

confidence: 64%

High carrier concentration in high Al‐composition AlGaN‐channnel HEMTs

Hashimoto

Akita

Yamamoto

et al. 2011

Phys. Status Solidi C

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High Al‐composition (Al = 51%) and low Al‐composition (Al = 20%) AlGaN‐channel high‐electron‐mobility transistors (HEMTs) on AlN layers with very high carrier concentration were demonstrated. In two types of HEMTs, 2‐dimensional electron gases (2DEG) were clearly observed and peak carrier concentration and sheet carrier concentration were approximately 1020 cm‐3 and higher than 2 × 1013 cm‐2, respectively. From the X‐ray diffraction (XRD) measurements, it was observed that the AlGaN channel layers on the AlN layers were partially relaxed and the degree of relaxation decreased with increasing Al‐composition of AlGaN channel layers. Therefore the misfit dislocations in the high Al‐composition HEMTs were considered to be lower than those in the low Al‐composition HEMTs. Furthermore, it was revealed that very high Al‐composition of AlGaN barrier layers can be grown coherently on the AlGaN channel layers in consequence of the partly relaxation of the AlGaN channel layers, which of lattice constants of a‐axis were smaller than that of fully relaxed AlGaN channel layers. Therefore very high carrier concentration of 2DEG can be obtained in spite of the high Al‐composition of AlGaN channel layers. We considered that this high carrier concentration of 2DEG was necessary to demonstrate high Al‐composition AlGaN‐channel HEMTs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…5,6 Owing to their wide bandgap and excellent thermal stability and conductivity, AlN templates on heterosubstrates such as sapphire, silicon carbide, and silicon have been promising candidates for growth of AlGaN. 3,7,8 However, due to the large lattice mismatch and thermal expansion coefficient differences between AlN and the substrate, growth of AlN templates still suffers from high-density threading dislocations as well as poor surface morphology. To achieve high-quality AlN templates, many approaches such as the ammonia pulse-flow multilayer growth method and pulsed atomic layer epitaxy (PALE) have been proposed, and great progress has been made.…”

Section: Introductionmentioning

confidence: 99%

The Effect of AlN Nucleation Temperature on the Growth of AlN Films via Metalorganic Chemical Vapor Deposition

Wang

Xiong

et al. 2011

Journal of Elec Materi

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AlN epilayers were grown directly on sapphire (0001) substrates using a combined growth scheme, consisting of a low-temperature nucleation layer and a second layer grown by high-temperature pulsed atomic layer epitaxy via metalorganic chemical vapor deposition. With an emphasis on the nucleation layer, its growth temperature was varied from 470°C to 870°C, and obvious differences in the surface morphology, crystal quality, and strain states of the overall AlN epilayers were observed. Based on atomic force microscopy, x-ray diffraction, and Raman spectroscopy results, these differences are ascribed to the nucleation sites and the subsequent grain size. Due to the enhanced mobility of Al adatoms with increasing temperature, the nucleation sites decrease and the subsequent grain size increases, leading to the achievement of atomically flat AlN epilayers with good crystal quality for the nucleation layer grown at 570°C. However, at higher nucleation layer growth temperature, the properties of the AlN epilayers deteriorate due to the possible appearance of misaligned AlN grains. A model is also developed according to all observations.

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Relaxation and recovery processes of AlxGa1−xN grown on AlN underlying layer

Cited by 15 publications

References 11 publications

TEM study of defects in AlxGa1−xN layers with different polarity

TEM study of defects in AlxGa1−xN layers with different polarity

High carrier concentration in high Al‐composition AlGaN‐channnel HEMTs

The Effect of AlN Nucleation Temperature on the Growth of AlN Films via Metalorganic Chemical Vapor Deposition

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