Seeded growth process for preparing aluminum nitride single crystals

A method of securing a single crystal seed to a crucible for use in a crystal growth process, the method comprising:

• providing a crucible comprising a crucible body defining an open-ended chamber and a removable cap adapted for closing the open end of the chamber;
• placing an AlN source material within the crucible chamber;
• subliming the AlN source material within the crucible, said subliming step comprising heating the crucible chamber in a manner sufficient to establish an axial temperature gradient between the AlN source material and an internal surface upon which a condensed polycrystalline mass of the AlN source material is to be deposited, the AlN source material being maintained at a higher temperature than the deposition surface, said heating step causing the deposition of a condensed polycrystalline mass of the AlN source material on the internal surface of the crucible chamber;
• placing a single crystal AlN seed on a surface of the removable cap facing the interior of the crucible chamber following said subliming step;
• closing the open end of the crucible chamber with the removable cap carrying the seed;
• and
• heating the crucible chamber containing the condensed polycrystalline mass of AlN source material approximately isothermally to a temperature sufficient to fuse the seed to the crucible cap.

A method of securing a single crystal seed to a crucible for use in a crystal growth process, the method comprising:

• providing a crucible comprising a crucible body defining an open-ended chamber and a removable cap adapted for closing the open end of the chamber;
• placing an AlN source material on the cap of the crucible with the crucible in an inverted position;
• while maintaining the crucible in an inverted position, subliming the AlN source material within the crucible for a time and at a temperature sufficient to deposit a condensed polycrystalline mass of the AlN source material on an internal surface of the crucible chamber;
• placing a single crystal seed on a surface of the removable cap facing the interior of the crucible chamber with the crucible in an inverted position, the polycrystalline mass of AlN source material being positioned above the seed;
• and
• while maintaining the crucible in an inverted position, heating the crucible chamber containing the condensed polycrystalline mass of AlN source material to a temperature sufficient to fuse the seed to the crucible cap.