The selective overgrowth method was used to grow bulk-like GaN layers by sublimation, and Si and SiO2 (which had a different evaporation rate, thermal conductivity, and thermal expansion coefficient) were chosen as masks. The effect of various masking materials upon the reduction of dislocation density was studied. The lateral growth rates depended strongly upon the direction of the mask stripe. For stripe windows which were aligned in the GaN<1¯1•0> direction, the lateral growth rate was approximately 4 times higher than with the stripe direction in the GaN<11•0> direction. The microstructure of selectively re-grown GaN was investigated by means of transmission electron microscopy, scanning electron microscopy and cathodoluminescence techniques. The threading dislocations in the region of laterally re-grown nitride were extended in 2 different ways. Firstly, the threading dislocations propagated perpendicularly into the top surface in the window region. In this case, the density of threading dislocations was about 109/cm2 within the window regions of the mask, and was reduced to 106/cm2 in the lateral overgrowth region of the mask; due to the termination of further dislocation propagation by the mask. Secondly, the propagation direction of the dislocations became parallel to the c-plane in laterally overgrown nitride, and became perpendicular to the plane in the middle region of the mask.

Lateral overgrowth mechanisms and microstructural characteristics of bulk-like GaN layers J.Wang, R.S.Q.Fareed, M.Hao, S.Mahanty, S.Tottori, Y.Ishikawa, T.Sugahara, Y.Morishima, K.Nishino, M.Osinski, S.Sakai: Journal of Applied Physics, 1999, 85[3], 1895-9