Mass transfer in A1N crystal growth at high temperatures

A one-dimensional mass transfer model based on equilibrium sublimation and gas phase diffusion was developed for high-temperature sublimation growth of AIN in an RF heated reactor and validated with growth results. The model predicted the apparent activation energy for growth to be close to the energy of sublimation. Using the model-predicted growth conditions, a 25 min diameter polycrystalline boule was grown at a rate of 1 mm/h. Growth was performed at short source-to-seed distances (similar to 10 min), nitrogen pressure of 600 Torr, nitrogen flow-rate of 100 sccm, and source temperatures ranging from 2000degreesC to 2400degreesC. Fast grain size development was achieved in the growth direction. The grown material was transparent and virtually colorless. (C) 2004 Elsevier B.V. All rights reserved.