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Study on the sources of stress in HVPE-GaN layer crystallized on 1-in. ammonothermally grown GaN seed is presented in this paper. Characterization by means of X-ray diffraction and transmission electron microscopy is performed. HVPE-GaN samples of high quality and those with visible quality deterioration are investigated on c-plane and m-plane cross-sections. Special attention is paid to HVPE material growing in semi-polar and non-polar directions on the edges of the seed and the growing layer. It is shown that this material generates significant stress leading to a structural deterioration of HVPE-GaN growing in the c -direction. [ABSTRACT FROM AUTHOR]

GaN/AlGaN quantum wells (QWs) were grown by metal–organic vapor phase epitaxy (MOVPE) on c -, a -, m -, and (20.1)-plane GaN substrates obtained by the ammonothermal method in the same MOVPE process, i.e. a process with growth parameters optimized for c -plane GaN templates. The structural properties of GaN/AlGaN QWs were carefully investigated by high angle annular dark field scanning transmission electron microscopy. Sharp GaN/AlGaN interfaces were seen for QWs grown on the c -, a -, and m -plane GaN substrates, but very rough interfaces with {1-100} and {1-101} facets were observed on the (20.1)-plane GaN substrate. In addition, the Al-rich region of AlGaN and GaN transition was identified for each of the GaN/AlGaN QW samples deposited in this process. The thickness and composition of this region varied with the crystallographic orientation of GaN substrates. [ABSTRACT FROM AUTHOR]

One of the main advantages of the hydride vapor phase epitaxy (HVPE) method for crystallizing bulk gallium nitride is the crystallization of GaN with a relatively high growth rate (>100 μm/h). In this paper various growth rates in the c -direction during crystallization of GaN by HVPE on ammonothermally grown GaN crystals are determined and examined. The influence of the highest (380 μm/h) and the lowest (40 μm/h) growth rate on the structural quality and purity of the HVPE-GaN crystals is analyzed. The optimal macroscopically stable growth rate (without cracks and pits) and the way of achieving it are presented and discussed. [ABSTRACT FROM AUTHOR]

The results of the Hydride Vapor Phase Epitaxy (HVPE) on ammonothermal GaN seeds (Am-GaN) with various misorientations: 0.3, 0.5 and 1 degree to the [1 0 −1 0] and [1 1 −2 0] directions are presented. Growth rate and structural quality of the HVPE-GaN layers are analyzed. Morphology of the crystal growing surface at the beginning of the crystallization process (after one and two hours of growth) and at the end of it (after eight hours) is presented as a function of the Am-GaN seed misorientation. Based on these results a rough growth model is proposed and discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present progress made recently in the development of the growth of truly bulk GaN crystals by the ammonothermal method in basic environment. High quality 2-in c-plane GaN seeds are shown. Non-polar wafers can also be cut out from thick GaN crystals grown by ammonothermal method. Perfect crystallinity manifests in very narrow peaks in X-ray rocking curves (the full width at half maximum equals about 15arcsec). GaN epilayers deposited on these substrates exhibit intrinsic narrow exciton lines, which are very sensitive to the optical selection rules typical for hexagonal symmetry, proving the truly non-polar character of such AMMONO-GaN substrates. Other challenges like homogenous insulating properties or high p-type conductivity have been also accomplished by means of ammonothermal method. Semi-insulating crystals of resistivity up to 1011 Ωcm and p-type conductivity within hole concentration up to 1018 cm−3 are already available in diameters up to 1.5-in. [ABSTRACT FROM AUTHOR]