Papers by Keyword: PVT Bulk Growth

Abstract: A systematic study on the density and distribution of extended defects in a typical single crystal AlN boule grown by the physical vapor transport (PVT) method has been carried out in order to gain a detailed understanding of the formation of defects such as dislocations and low angle grain boundaries (LAGBs). Boule surface studies reveal that LAGBs are nucleated during initial stages of growth and propagate to the end of growth. Basal plane dislocations (BPDs) are generated during growth due to thermal gradient stresses. Higher BPD densities are found near the LAGBs at the boule edges due to additional stresses from constrained growth. Threading edge dislocations (TEDs) are typically replicated from the seed, and LAGBs composed of arrays of threading dislocation walls are formed to accommodate the c-axis rotation between different groups of threading screw dislocation (TSD) mediated growth centers.

Abstract: The ability to set and accurately control the desired growth conditions is crucial in order to attain high quality bulk growth of Silicon Carbide (SiC), especially when the ingot size is large (> 2” in diameter by > 2” long). However, these two aspects of SiC PVT (Physical Vapor Transport) growth technology are severely limited in “conventional” SiC PVT growth reactors with single cylindrical heaters. To overcome such shortcomings, an “alternative” furnace design with two plane resistive heaters is proposed. In order to verify benefits of this design, numerical modeling and comparative procedures have been employed. Detailed comparative analysis revealed two fundamental disadvantages of the conventional furnace design, attributed to (a) – significantly higher in magnitude and spatially nonuniform distribution of the thermal stress that consequently deteriorates structural quality of the growing SiC boule, and (b) – inability to grow long (> 2”) monocrystalline ingots of SiC. Furthermore, the potential of the alternative furnace design to overcome fundamental limitations of the conventional design is also analyzed, with particular attention being paid to the processes of source material recrystallization.