Dependance of hot-zone position on AlN single crystal growth by PVT method

AlN single crystals were grown by the PVT (Physical vapor transport) method with position-changable induction coil. And the graphite crucible dimensioned Phi 90xH120 was used on processing. The temperature was 1950 similar to 2050 degrees C and ambient pressure was 150 similar to 1 Torr. And the hot-zone was changed according to times on growing for result comparison. When hot-zone by coil is located below far enough (>40 mm) from AlN crystal concentration position, the as-grown crystals physical size is better (300 mu m/hr) than another condition, but the condition-reproducibility was very poor. However the closer the distance between hot-zone and AlN growing posion, the smaller the size of as-grown crystal and the rarer the generation of the crystal nuclear, but the crystal growing condition is stable for quality. The best condition for both growth rate and quality is gained when the starting position of hot-zone coil is about 20 mm distance from growing position. For the best growth condition, the position of hot-zone is very sensitive factor and the further more the condition of speed of coil shift also must control.