Characterization of crystal lattice constant and strain of GaN epilayers with different AlxGa1-xN and AlN buffer layers grown on Si (111)

Hexagonal GaN epilayers with different AlxGa1-xN and AIN buffer layers were grown on Si(111) by metal-organic vapor phase epitaxy (MOVPE). Under the same growth conditions, the sample with four AlxGa1-xN buffer layers and one AIN buffer layer were grown on Si(111). According to the results of Rutherford backscattering (RBS)/channeling along less than or equal 0001>) axis, the conventional ??-2?? scans normal to GaN(0002) and (112 over-bar 2) plane at 0?? and 180?? azimuthal angles, and the reciprocal-space X-ray mapping (RSM) on GaN(101 over-bar 5) plane, we obtained that the crystal quality of the GaN epilayer is perfect with Xmin = 1.54%. The crystal lattice constant of AIN, AlxGa1-xN and GaN epilayer has been calculated accurately, the lattice constant of GaN epilayer is almost equal to the theoretic data (aepi = 0.31903 nm, cepi = 0.51837 nm). The tetragonal distortion along the depth can got clearly from elastic strains of each layer in the normal and parallel directions, and the tetragonal distortion of GaN epilayer is nearly fully relaxed(eT = 0).EI062977-29815