An investigation was made of bulk GaN grown by HVPE either in the conventional polar [00•1] direction and subsequently sliced with non-polar surfaces or grown in the non-polar [11•0] direction. Spatially resolved techniques such as cathodoluminescence imaging and transmission electron microscopy, as well as profile measuring techniques such as positron annihilation spectroscopy and secondary ion mass spectroscopy were employed to directly visualize the extended structural defects, and point defect (impurity and vacancy) distributions along the growth axes. A comparative analysis of the results shows a distinctive difference in the distribution of all kind of defects along the growth axes. A significant decrease in the defect density in material grown along the polar direction, in contrast to the constant behavior of the high defect density in material grown along the non-polar direction points out the low-defect superior quality of the former material and indicated the preferable way of producing high-quality GaN substrates with non-polar surfaces.

Defect and Emission Distributions in Bulk GaN Grown in Polar and Nonpolar Directions - a Comparative Analysis. T.Paskova, A.Hanser, E.Preble, K.Evans, R.Kröger, F.Tuomisto, R.Kersting, R.Alcorn, S.Ashley, C.Pagel, E.Valcheva, P.P.Paskov, B.Monemar: Proceedings of the SPIE, 2008, 6894, 68940D