Sublimation growth of bulk AIN crystals: process temperature and growth rate

This study was made to estimate the temperature range for AlN growth by sublimation and to evaluate the rate-limiting step in order to achieve bulk growth at practically useful rates. Growth experiments have been conducted in a proprietary designed reactor capable up to 2500degreesC in vertical transport geometry. PVT transport of AlN was found to be feasible in a wide range of temperature starting from 1850degreesC, but stable growth of well-faceted crystals was possible only at temperatures exceeding 2100degreesC. Quick material transport in combination with insufficient crucible integrity at said temperatures is a crucial problem and the main size-limiting factor in PVT growth of AlN. Polycrystalline boules up to two inch in diameter and up to 15 mm produced at growth rates 0.3-3.0 mm/h have been demonstrated. Grown material is a theoretically dense, highly pure (below 100 ppm of oxygen), textured bulk containing single-crystalline areas larger than 5x5 mm(2).