Tetragonal Distortion of GaN Epilayer with Multiple Buffer Layers on Si (111) Studied by RBS/Channelling and HRXRD

Rutherford backscattering (RBS)/channelling and high resolution x-ray diffraction (HRXRD) have been used to characterize the tetragonal distortion of a GaN epilayer with four Al_xGa _1-x N and single AlN buffer layers grown on a Si (111) substrate by metal-organic vapour phase epitaxy (MOVPE). The results show that a 1000nm GaN epilayer with a perfect crystal quality (χ_min=1.54%) can be grown on the Si (111) substrate in virtue of multiple buffer layers. Using the RBS/channelling angular scan around an off-normal <1 213> axis in the (1010) plane and the conventional HRXRD θ-2θ scans normal to GaN (0002) and (1122) planes at the 0° and 180° azimuth angles, the tetragonal distortion e_T, which is caused by the elastic strain in the epilayer and different buffer layers, can be obtained respectively. The two experiments are testified at one result, the tetragonal distortion of GaN epilayer is nearly to a fully relaxed (e_T=0).