Influence of the V/III ratio in the gas phase on thin epitaxial AlN layers grown on (0001) sapphire by high temperature hydride vapor phase epitaxy

Claudel, A.; Fellmann, V.; Gélard, Isabelle; Coudurier, Nicolas; Sauvage, D.; Balaji, M.; Blanquet, Elisabeth; Boichot, R.; Beutier, G.; Coindeau, S.; Pierret, Aurélie; Attal‐Trétout, Brigitte; Luca, Sorana; Crisci, Alexandre; Baskar, K.; Pons, M.

doi:10.1016/j.tsf.2014.11.022

Cited by 27 publications

(23 citation statements)

References 45 publications

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“…It appears that at the proximity of the interface between the substrate and the buffer, the Al 2 O 3 manifests a disordered microstructure and because of the substrate effect on the buffer, a high density of dislocations can be found inside the AlN structure. A slight nitrogen diffusion outside the AlN buffer boundary towards the substrate can be identified, suggesting an exchange of oxygen with nitrogen atoms at the surface of the sapphire (nitridation of the sapphire substrate), which might locally affect the crystallographic relationship of growth, a phenomenon similar with the findings of Claudel et al [23] and Miyagawa et al [24]. Their theory was based on the formation of phase inversion domains (ID) that usually occurs when an Al(O,N) interlayer is present.…”

Section: Microstructural Characterizationsupporting

confidence: 81%

Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

et al. 2019

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This study assesses the characteristics (edge and screw dislocation density) of a commercially available GaN/AlN/Al2O3 wafer. The heterostructure was evaluated by means of high-resolution X-ray diffraction (HR-XRD), high-resolution transmission electron microscopy (HR-TEM), and Doppler-Broadening Spectroscopy (DBS). The results were mathematically modeled to extract defect densities and defect correlation lengths in the GaN film. The structure of the GaN film, AlN buffer, Al2O3 substrate and their growth relationships were determined through HR-TEM. DBS studies were used to determine the effective positron diffusion length of the GaN film. Within the epitaxial layers, defined by a [GaN P 63 m c (0 0 0 2) || P 63 m c AlN (0 0 0 2) || (0 0 0 2) R 3 ¯ c Al2O3] relationship, regarding the GaN film, a strong correlation between defect densities, defect correlation lengths, and positron diffusion length was assessed. The defect densities ρ d e = 6.13 × 1010 cm−2, ρ d s = 1.36 × 1010 cm−2, along with the defect correlation lengths Le = 155 nm and Ls = 229 nm found in the 289 nm layer of GaN, account for the effective positron diffusion length Leff~60 nm.

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Section: Microstructural Characterizationsupporting

confidence: 81%

Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

et al. 2019

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“…Among various approaches for high-quality AlN grown on sapphire substrates, e.g. multilayer growth [2,6,7] or high-temperature annealing of AlN films [8,9], the deposition by hydride vapour phase epitaxy (HVPE) [10,11] and the growth on nano-patterned sapphire substrates (nano-PSS) by metalorganic vapour phase epitaxy (MOVPE) [12][13][14][15] have been shown to be promising. However, the AlN surface morphology caused by the last two techniques is often defined by macrosteps [11,[13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Reduction of surface roughness by modification of step-bunched aluminum nitride layers towards step-flow morphology

Tillner¹,

Brandl²,

Hoffmann³

et al. 2020

physics

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Conventional aluminum nitride (AlN) template fabrication techniques, like hydride vapour phase epitaxy or AlN growth on patterned sapphire substrates, usually lead to step-bunched template surfaces. The resulting macrosteps cause emission broadening or even multiple-peak characteristics of ultraviolet light-emitting diodes (UV LEDs) fabricated on such AlN templates. In order to reduce these macrosteps and to provide a smoother surface, even without the need of a thick AlN deposition, a two-layer growth procedure is reported here. A three-dimensional (3D) – twodimensional (2D) sequential growth initiates a significant modification of the previous AlN surface morphology and simultaneously limits the evolving tensile strain. A primarily step-bunched surface with a surface roughness root mean square of 1.8 nm is successfully reduced by the two-layer growth procedure down to 0.8 nm, without any film cracking. This distinct roughness reduction of more than 50% is achieved within an AlN thickness of only 1.3 µm. With a smoother surface, the electroluminescence characteristic of a UV LED structure is substantially improved. Instead of a double-peak emission, typical for LEDs grown on step-bunched templates, a single-peak emission and lower spectral width were achieved, indicating the high potential of the suggested two-layer technique for improving performance.

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“…Extensive studies have been carried out on the growth optimization of the AlN films on sapphire. In particular, the initial growth conditions including hydrogen (H2) annealing [7], growth temperatures [8,9], thickness control of the nucleation layers (NLs) [10,11], and the III/V ratio [12] have shown significant impacts on the surface morphology, polarity and crystal quality of the MOCVD-grown AlN films. Inappropriate growth temperatures and thicknesses of the NL could lead to generating mixed polarities and inversion domains in AlN films.…”

Section: Introductionmentioning

confidence: 99%

Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

Sun

Tahtamouni

et al. 2017

J. Phys. D: Appl. Phys.

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The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0001) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al-(N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

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Influence of the V/III ratio in the gas phase on thin epitaxial AlN layers grown on (0001) sapphire by high temperature hydride vapor phase epitaxy

Cited by 27 publications

References 45 publications

Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

Reduction of surface roughness by modification of step-bunched aluminum nitride layers towards step-flow morphology

Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

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