AbstractNonpolara-plane GaN films were grown on r-plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy. The as-grown layers were studied by high-resolution x-ray diffraction. Thea-plane GaN lattice mosaic is orientation dependent as determined by x-ray rocking curve (XRC) measurements. The tilt mosaic measured with the c-axis within the scattering plane (c-mosaic) was greater than the mosaic measured with the m-axis within the scattering plane (m-mosaic). The mosaic along both azimuths decreased and thec-mosaic/m-mosaic ratio was increased with increase of growth temperature from 1050 °C to 1080 °C. The morphological transition was correlated to change in thea-plane GaN tilt mosaic measured by XRC.
AbstractWe report on AlN wafers fabricated by hydride vapor phase epitaxy (HVPE). AlN thick layers were grown on Si substrates by HVPE. Growth rate was up to 60 microns per hour. After the growth of AlN layers, initial substrates were removed resulting in free-standing AlN wafers. The maximum thickness of AlN layer was about 1 mm. AlN free-standing single crystal wafers with a thickness ranging from 0.05 to 0.8 mm were studied by x-ray diffraction, transmission electron microscopy, optical absorption, and cathodoluminescence.
AbstractWe report a structural analysis of GaN layers with thicknesses ranging from 10 μm to 250 μm which have been grown on sapphire substrates by halide vapor phase epitaxy (HVPE). The effect of growth rate during HVPE growth has also been examined. The growth was performed using GaCl and ammonia as reactants; growth rates in excess of 90 μm/hr have been achieved. The structural characteristics of these layers have been performed wit'i high resolution x-ray diffractometry. Longitudinal scans parallel to the GaN [0002] direction, transverse scans perpendicular to the [0002], and reciprocal space maps of the total diffracted intensity have been obtained from a variety of GaN layers. The transverse scans typically show broad rocking curves with peak breadths of several hundreds of arcseconds. In contrast, the longitudinal scans (or “θ/2θ scans”) which are sensitive only to strains in the GaN layers (and not their mosaic distributions) showed peak widths that were at least an order of magnitude smaller and in some cases were as narrow as 16 arcseconds. These results suggest that the defect structure of the GaN layers grown by HVPE is dominated by a dislocation-induced mosaic distribution, with the effects of strain in these materials being negligible in comparison.
ABSTRACTHigh resolution x-ray diffraction and x-ray topography study of GaN thin films, grown on sapphire (00.1) substrate by reduced pressure metalorganic vapor phase epitaxy under various conditions, were performed. An attempt was made to correlate the mobility in films with similar carrier concentration with the strain and dislocation density. X-ray topography revealed the defects present in the film.
We report on AlN wafers fabricated by hydride vapor phase epitaxy (HVPE). AlN thick layers were grown on Si substrates by HVPE. Growth rate was up to 60 microns per hour. After the growth of AlN layers, initial substrates were removed resulting in free-standing AlN wafers. The maximum thickness of AlN layer was about 1 mm. AlN free-standing single crystal wafers with a thickness ranging from 0.05 to 0.8 mm were studied by x-ray diffraction, transmission electron microscopy, optical absorption, and cathodoluminescence.
AlN Wafers Fabricated by Hydride Vapor Phase Epitaxy