RAMAN AND PHOTOLUMINESCENCE STUDIES OF BIAXIAL STRAIN IN GAN EPITAXIAL LAYERS GROWN ON 6H-SIC

The effect of biaxial strain on optical phonons in high-quality GaN ep itaxial layers grown on 6H-SiC substrates by metal organic chemical va por deposition has been studied. The deformation potential constants f or the E-2((1)), A(1)(TO), E-1(TO), and E-2((2)) optical phonon modes in hexagonal GaN have been obtained. A method for calculating strain i n hexagonal GaN layers from Raman data alone is suggested. A comparati ve analysis of the strain measured by x-ray diffraction and Raman spec troscopy shows that these data agree well. It is found that the biaxia l stress of 1 GPa results in a shift of the excitonic photoluminescenc e lines of 20 +/- 3 meV. (C) 1997 American Institute of Physics.