Methods for controllable doping of aluminum nitride bulk crystals

A method of forming polycrystalline AlN, the method comprising the steps of:

• providing within a crucible a pellet comprising Al, the crucible comprising a foil wrap;
• reacting the pellet at a reaction temperature and a reaction pressure with nitrogen gas to form a bulk polycrystalline AlN ceramic, wherein, when the polycrystalline AlN ceramic reaches approximately room temperature after the reaction, the polycrystalline AlN ceramic having properties including (i) less than approximately 1% excess Al and (ii) an oxygen concentration of less than approximately 100 ppm;
• after forming the polycrystalline AlN ceramic, and with no sublimation-recondensation treatment of the polycrystalline AlN ceramic therebetween, providing the polycrystalline AlN ceramic and at least a portion of the foil wrap at a first end of and within a crystal growth enclosure;
• subliming the polycrystalline AlN ceramic at a formation temperature, the at least a portion of the foil wrap remaining in contact with the polycrystalline AlN ceramic thereduring;
• and
• forming an AlN single crystal at a second end of the crystal growth enclosure.