Effect of Initial Growth Conditions on The Strain in a-plane GaN

The effect of nitridation treatment and the low temperature(LT) AlN buffer on structure and strain of a-plane GaN epilayers grown on r-plane sapphire by low pressure metalorganic chemical vapor deposition(LP-MOCVD) has been investigated by high resolution X-ray diffraction(HRXRD) and polarized Raman scattering spectra in backscattering configurations.For the sample using the LT-AlN buffer,the full widths at half maximum(FWHM) of X-ray rocking curves(XRC) and the strain of a-plane GaN are lower comparing with that of the sample with nitridation,which is consistent with the smaller in-plane stress anisotropic distribution in a-plane GaN epilayers with LT-AlN buffer.