It was recalled that GaN could have a sphalerite structure (cubic-GaN) or a wurtzite structure (hexagonal GaN). A H-GaN epilayer with a low-temperature AlN buffer layer was grown onto Si(111) substrates by metal-organic chemical vapour deposition. According to the full-width at half-maximum values of 0.166° and 14.01/cm of HDXRD curve and E2 (high) phonon of Raman spectrum respectively, it was found that the crystal quality was perfect. Based upon the X-ray diffraction spectrum, the crystal lattice constants of Si (a = 5.3354Ǻ) and H-GaN (aepi = 3.214Ǻ, cepi = 5.119Ǻ) were calculated for researching the tetragonal distortion of the sample. These results indicated that the GaN epilayer was in tensile strain and Si substrate was in compressive strain; in good agreement with the analysis of Raman peak shifts. Typical values of screw-type (Dscrew = 7 x 108/cm2) and edge-type (Dedge = 2.9 x 109/cm2) dislocation density, were larger than those in GaN epilayers growth onto SiC or sapphire substrates. These findings were important for the understanding and application of nitride semiconductors.

Characterization of Crystal Lattice Constant and Dislocation Density of Crack-Free GaN Films Grown on Si(111). J.Xiong, J.Tang, T.Liang, Y.Wang, C.Xue, W.Shi, W.Zhang: Applied Surface Science, 2010, 257[4], 1161-5