Sublimation growth of AlN in vacuum and in a gas atmosphere

The growth of AIN crystals by sublimation technique is investigated. Two mechanisms of Al and N-2 transport from the source to the seed are distinguished - occurring predominantly via diffusion or via drift of the reactive species. Drift transport provides considerably higher growth rates compared to diffusive transport. The interplay of these mechanisms depends on temperature and gas pressure in the growth system. A theoretical model of ALN sublimation growth is developed allowing one to estimate the growth rate as a function of gas pressure and temperature. The theoretical predictions agree well with experimental observations obtained while growing AIN in the nitrogen atmosphere and in vacuum.