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A high-quality thick AlN layer without cracks was grown on sapphire by the combination of the high-temperature metal-organic vapor phase epitaxial growth and epitaxial lateral overgrowth methods. The dislocation behavior and growth mode of AlN are investigated in detail. The dislocation density of the AlN layer thus grown was less than 107cm−2.

Epitaxial lateral overgrowth (ELO) of low‐dislocation‐density AlN layers on trench‐patterned sapphire substrates is demonstrated for the first time. Sapphire (0001) substrates with trench patterns formed along two different directions, 〈10$ 10 \bar 10 $0〉 and 〈11$ 11 \bar 20 $0〉, were used. We can obtain fully coalesced AlN only on the sapphire substrate having 〈11$ 11 \bar 20 $0〉 trenches. The dislocation density of ELO‐AlN is as low as 6.7 × 108 cm–2. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

AlN layers were grown by high-temperature MOVPE. A systematic analysis of high-temperature growth of AlN was carried out and the resultant layers were analyzed by X-ray diffraction and atomic force microscopy. The structural quality and the morphology of AlN layers improve with rising growth temperature.1 Introduction Dramatic improvement of the crystalline quality of GaN grown on a sapphire substrate by the low-temperature buffer layer technique [1] and control of the conductivity of the nitrides [2][3][4] have led to the evolution of high-efficiency optoelectronic devices in the visible short-wavelength region. Group III nitride semiconductors are promising potential for optoelectronic applications, particularly in the UV region. In order to realize UV-optoelectronics applications, it is necessary to grow highcrystalline-quality AlN.The main emphasis in this study is to grow better quality AlN layers by metalorganic vapor phase epitaxy (MOVPE). Among the prominent nitride semiconductors such as, GaN, AlN, InN and their alloys, with the notable exception of AlN and its alloys, layers of high-quality most of the materials can be grown at temperatures of 1200 °C or less. The crystalline quality of AlN layers is always inferior to its counterpart GaN grown at much lower temperatures. The high temperature growth of AlN films is expected to be effective in improving crystalline quality and surface morphology because surface migration of Al-species would increase at high temperatures. There are few reports on AlN growth at high temperatures on the order of 1350 °C [5,6] due probably to the instrumental limitation.In this study, we made an attempt to systematically study the high-temperature growth of AlN on (0001) sapphire substrates. The temperatures are in the range from 1200 to 1500 °C. In addition, the influence of the V/III ratio on the growth rate of AlN was observed by performing growth at three different values of the V/III ratio.

The metalorganic vapor phase epitaxial (MOVPE) growth of AlGaN on AlN-coated sapphire at a temperature higher than 1,200 °C was carried out. Compared with that at a low-temperature growth regime in which alloy composition is determined by the flow rates of metalorganic Ga and Al sources, the solid composition of AlGaN is found to be strongly affected by thermodynamics.