AlN heteroepitaxy on sapphire by metalorganic vapour phase epitaxy using low temperature nucleation layers

Li, Haoning; Sadler, Thomas C.; Parbrook, P. J.

doi:10.1016/j.jcrysgro.2013.08.024

Cited by 38 publications

(38 citation statements)

References 25 publications

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“…Such surface morphology is undesirable for the fabrication of high-quality heterostructures [25]. A similar surface morphology was also observed by a recent study by Li et al, who reported growing the AlN template layer at 1250 1C [24]. The formation of macro-steps can be attributed to a thermodynamic process wherein the mobility of Al atoms was high enough that the diffusion length of Al atoms was longer than the atomic step terrace width at high temperature [26].…”

Section: Resultssupporting

confidence: 68%

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Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition

Wei

Wang

et al. 2015

Journal of Crystal Growth

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a b s t r a c tWe studied temperature dependence of crystalline quality of AlN layers at 1050-1250 1C with a fine increment step of around 18 1C. The AlN layers were grown on c-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD) and characterized by X-ray diffraction (XRD) ω-scans and atomic force microscopy (AFM). At 1050-1068 1C, the templates exhibited poor quality with surface pits and higher XRD (002) and (102) full-width at half-maximum (FWHM) because of insufficient Al atom mobility. At 1086 1C, the surface became smooth suggesting sufficient Al atom mobility. Above 1086 1C, the (102) FWHM and thus edge dislocation density increased with temperatures which may be attributed to the shorter growth mode transition from three-dimension (3D) to twodimension (2D). Above 1212 1C, surface macro-steps were formed due to the longer diffusion length of Al atoms than the expected step terrace width. The edge dislocation density increased rapidly above 1212 1C, indicating this temperature may be a threshold above which the impact of the transition from 3D to 2D is more significant. The (002) FWHM and thus screw dislocation density were insensitive to the temperature change. This study suggests that high-quality AlN/sapphire templates may be potentially achieved at temperatures as low as 1086 1C which is accessible by most of the III-nitride MOCVD systems.

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Section: Resultssupporting

confidence: 68%

“…However, with insufficient TMAl pre-conditioning in our 3 Â 2 in. CCS MOCVD reactor, the surface of the AlN/sapphire template becomes rough and hazy, which is attributed to the mixed polarity AlN [23,24], as exemplarily exhibited in Fig. 1.…”

Section: Methodsmentioning

confidence: 84%

Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition

Wei

Wang

et al. 2015

Journal of Crystal Growth

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“…As presented in our previous work 21 , a three step temperature variation recipe was used to grow the films to a thickness of 2 µm in the MOVPE reactor. The 2" AlN wafers were cut into halves for subsequent processing.…”

Section: Methodsmentioning

confidence: 99%

“…These conditions were essentially the same as used for our thick planar AlN deposition. 21 For comparison two nanorod samples (no overgrowth) were also annealed in the reactor at 1100 C under a flow of NH3. In-situ reflectance measurements were carried out using a Laytec EpiTT system to monitor the growth.…”

Section: Methodsmentioning

confidence: 99%

“…The TDD of the coalesced AlN films were compared to optimised 3-step AlN grown layers previously obtained. 21 Without nanorod patterning the observed density of the edge and mixed dislocations was typically found to be ~4.4  10 9 cm -2 , as highlighted in the image shown in figure 7(b). In comparison, AlN films produced using the nanorod ELOG process had TDDs of < 10 8 cm -2 , as highlighted in the TEM image shown figure 7(a).…”

Section: (A) (B)mentioning

confidence: 98%

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Epitaxial lateral overgrowth of AlN on self-assembled patterned nanorods

Conroy

Zubialevich

et al. 2015

J. Mater. Chem. C

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We report an inexpensive nanoscale patterning process for epitaxial lateral overgrowth (ELOG) in AlN layers grown by metal organic vapour phase epitaxy (MOVPE) on sapphire. The pattern was produced by an inductively coupled plasma etch using a self-assembled monolayer of silica spheres on AlN as the lithographic mask. The resulting uniform 1 [small mu ]m length rod structure across a wafer showed a massive reduction in threading dislocations (TDs) when annealed at 1100 [degree]C. Overgrowing homoepitaxial AlN on top of the nanorods, at a temperature of 1100 [degree]C, produced a crack free coalesced film with approximately 4 [small mu ]m of growth, which is formed at a much lower temperature compared to that typically required for microscale ELOG. The improved crystal quality, in terms of TD reduction, of the AlN above the rods was determined by detailed weak beam (WB) electron microscopy studies and showed that the threading dislocation density (TDD) was greatly reduced, by approximately two orders of magnitude in the case for edge-type dislocations. In situ reflectance measurements during the overgrowth allowed for thickness coalescence to be estimated along with wafer curvature changes. The in situ measurements also confirmed that tensile strain built up at a much slower rate in the ELOG AlN layer compared to that of AlN prepared directly on sapphire

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Polar and semipolar (112) InAlN layers grown on AlN templates using MOVPE

Dinh

Parbrook

2015

Physica Status Solidi (b)

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We report on metalorganic vapor phase epitaxial growth of InAlN layers on (0001) and (11true2‾2) AlN templates at different temperatures (725–800 °C). The indium content (8.0–15.2%) of the (11true2‾2) InAlN layers was found to be lower compared to that for the (0001) layers (9.0–23.0%). The higher indium content of the (0001) layers was attributed to a high density of small hillocks and a larger degree of relaxation. The small hillocks on the (0001) layer surface acted as quantum‐dot‐like structures that caused a stronger emission at longer wavelength compared to weaker emission at shorter wavelength from a “bulk” layer underneath. A large Stokes‐shift of about 300 and 480 meV was observed for the (0001) and (11̅22) layers, respectively. The larger shift of the (11true2‾2) layers was attributed to a higher degree of localization. The larger degree of localization and higher unintentional oxygen incorporation enhanced the luminescence intensity of the (11true2‾2) layers compared to that for the (0001) layers.

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AlN heteroepitaxy on sapphire by metalorganic vapour phase epitaxy using low temperature nucleation layers

Cited by 38 publications

References 25 publications

Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition

Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition

Epitaxial lateral overgrowth of AlN on self-assembled patterned nanorods

Polar and semipolar (112) InAlN layers grown on AlN templates using MOVPE

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