The diffusion of Ga species in the gas phase as well as on surfaces was studied during the selective area growth of AlGaN via low-pressure metalorganic vapor phase epitaxy. The experiments were performed on a trapezoidal stripe with a (00▪1) facet on the top and a (1¯1▪1) facet on the sides. It was found that the ridge growth on the facets was sensitive to the growth pressure, in agreement with numerical results. At a pressure of 100Torr, a uniform thickness of AlGaN alloy was obtained, but the alloy composition was not uniform. Exponential variation of the composition gave an effective diffusion length of Ga which was of the order of 0.7μm; independent of the growth pressure (figure 1).

The Surface Diffusion of Ga Species on an AlGaN Facet Structure in Low Pressure MOVPE. T.Narita, Y.Honda, M.Yamaguchi, N.Sawaki: Physica Status Solidi C, 2007, 4[7], 2506-9