Strain effects in GaN thin film growth

Strain effects in GaN thin film crystals are analyzed by Photoluminescence (PL), X-ray and Raman scattering. All three methods can be consistently used to monitor strain that depends on the choice of substrate and other parameters. The high amount of stress incorporated in GaN hetero-expitaxial samples causes confusion as to assignment of the PL lines of donor bound excitons and donor-acceptor transitions. Homo-epitaxially grown GaN films provide a reference for unstrained films. The PL line positions of the donor acceptor pair transitions are found to exhibit a different stress coefficient than the excitonic line.