A Comparison of GaN Epilayers with Multiple Buffer Layers and with a Single Buffer Layer Grown on Si(111) Studied by HRXRD and RBS/Channeling

Two hexagonal GaN epilayers (samples A and B) with multiple buffer layers and single buffer layer are grown on Si (111) by metal-organic vapour phase epitaxy (MOVPE). From the results of Rutherford backscattering (RBS)/channeling and high resolution x-ray diffraction (HRXRD), we obtain the lattice constant (a and c) of two GaN epilayers (a_A=0.3190nm, c_A=0.5184nm and a_B=0.3192nm, c_B=0.5179nm), the crystal quality of two GaN epilayers ( X_{min A}=4.87%, X_{min B}=7.35% along <1213> axis) and the tetragonal
distortion e_T of the two samples along depth (sample A is nearly fully relaxed, sample B is not relaxed enough). Comparing the results with the two samples, it is indicated that sample A with multiple buffer layers have better crystal quality than sample B with a single buffer layer, and it is a good way to grow GaN epilayer on Si (111) substrates using multiple buffer layers to improve crystal quality and to reduce lattice mismatch.