ABSTRACT
GaN epilayers grown on sapphire substrates nitridated for various lengthy periods were investigated by light scattering tomography (LST) and Raman scattering. In the LST images of the plane-view epilayers, the light scattering defects distribute in < 11 2 ¯ 0 > https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315140810/c990b9db-a87a-4526-ade7-32570fb656b8/content/eq133.tif"/> directions. The defect density is lower in epilayer grown on substrate nitridated for a longer period. The defects are believed to be straight threading edge dislocations on { 1 1 ¯ 00 } https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315140810/c990b9db-a87a-4526-ade7-32570fb656b8/content/eq134.tif"/> planes. The Raman shift of E2 mode is larger in the sample grown on substrate nitridated for a longer period. Our results show that the stress is higher in the sample with fewer dislocations.
