Control of AlN buffer/sapphire substrate interface for AlN growth

Abstract

The growth condition of AlN buffer layer has been studied in order to fabricate a high‐quality AlN layer on a sapphire substrate. The growth of high‐quality AlN is extremely difficult due to the weak surface migration of Al adatoms. Therefore we have focused on the AlN buffer layer, and examined the growth condition while controlling the thickness and growth temperature. The crystalline quality of the AlN layer grown on an AlN buffer layer at a growth temperature of 1250 °C was improved, and the full width at half‐maximum (FWHM) value of the X‐ray rocking curve (XRC) obtained for (0002) and (10‐10) diffractions were 138 and 464 arcsec, respectively. Moreover, AlOxN1‐x was formed when the AlN buffer layer was grown at a high temperature (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electron microscopy analysis of microstructure of postannealed aluminum nitride template

“…Several attempts to control the microstructure in a nucleation layer have been made in order to mitigate the formation of threading dislocations, but further improvement is required. 10,11) Some of the present authors 12) confirmed that postannealing at a high temperature is quite effective for producing a high-quality AlN template, revealing that the postannealed AlN has a two-layer structure. In this study, the microstructural evolution of the postannealed AlN was analyzed by atomic force microscopy (AFM) and transmission electron microscopy (TEM), and it was confirmed that the two-layer structure is made of inversion domains.…”

In situ observation of two-step growth of AlN on sapphire using high-temperature metal–organic chemical vapour deposition

“…[11][12][13][14] For each of these techniques, at least one of the source flows (metal-organic source or NH 3 ) is modulated to serve as an input to the reactor to enhance the Al atomic migration on the substrate surface, and thus improve the AlN quality. In addition, high-temperature (>1300 uC) MOCVD (HT-MOCVD) 15,16 or hydride vapor phase epitaxy 17 are the other choices for the growth of high-quality AlN films because high growth temperatures can also improve the migration of atomic Al on the substrate surface. However, until now, there have been few in situ observations of the AlN growth process because of technical limitations.…”

Microstructure of AlN Grown on a Nucleation Layer on a Sapphire Substrate

“…The band zone is about 2 nm in width and has reasonably sharp borders with AlN and sapphire, and the thickness of the interlayer for T NL ¼ 1250 C is thicker than that for T NL ¼ 1100 C. Details about the thickness of interlayer are reported in ref. 9. Influence of the interlayer thickness on the AlN polarity and the grain size is under investigation, which will be reported elsewhere.…”

“…Recently, control of a nucleation layer (NL) has been adopted by some research groups to obtain high-quality AlN. 8,9) In our previous study, 9) it was found that a 1-m-thick AlN layer grown on NL-AlN exhibited a smooth surface morphology when the growth temperature of NL-AlN was T NL ¼ 800 C. For T NL ¼ 1250 C, the crystallinity of AlN was improved significantly but the surface became rather rough; it was difficult to improve both the surface morphology and crystalline quality of AlN layer. In this study, we examined the growth conditions of NL-AlN to clarify their effects on the microstructure and growth process of the AlN layer.…”

“…As shown in the STEM-HAADF images photoelectron spectroscopy (XPS). 9) The exchange of oxygen atoms with nitrogen atoms might have locally affected the crystallographic polarity of the overgrown AlN. It is necessary to mitigate the formation of inversion domains to grow an AlN layer with a flat surface.…”