Structural Characterization of Bulk AlN Single Crystals Grown from Self-Seeding and Seeding by SiC Substrates
Using a combination of synchrotron white beam x-ray topography (SWBXT) and high resolution x-ray diffraction (HRXRD), the structural quality of AlN crystals grown by various sublimation-based techniques have been non-destructively analyzed. Spontaneously nucleated AlN crystals are characterized by very low defect densities but their size is small. Self-seeding results in nucleation of multiple grains of different orientations, a few of which are of good quality while most are highly strained. Using readily available commercial 4H and 6H-SiC substrates, several growth runs have been carried out using different growth conditions to obtain thick AlN layers, either attached to the seed or free-standing. While attached layers are typically cracked and highly strained, crack-free free-standing layers can be obtained by delamination or SiC decomposition. X-ray characterization reveals these crystals have good purity but moderately high defect densities.
Robert P. Devaty, David J. Larkin and Stephen E. Saddow
B. Raghothamachar et al., "Structural Characterization of Bulk AlN Single Crystals Grown from Self-Seeding and Seeding by SiC Substrates", Materials Science Forum, Vols. 527-529, pp. 1521-1524, 2006