High AI Content in Alx Gal1-x N on GaN Buffer/Sapphire Grown by RFMBE

In this work, we have successfully grown high quality AlxGa1-xN (400 nm) films with high Al contents (x = 0.5) on sapphire (0001) substrates with GaN (150 nm) buffer layers by radio frequency molecular beam epitaxy (RF-MBE). The relationship between the film quality and different AI contents will be discussed in depth. The X-ray diffraction (XRD) 20 peak of the AlGaN/GaN structure is 34.66 and 35.43 degree with 0.5 aluminum compositions. A degradation of the crystalline quality of AlGaN layers is observed with increasing Al contents. The 6.42 arcmin full-width at the half-maximum (FWHM) of XRD is better than those reported. The 2.985 nm surface roughness for 2 µm x 2 µm area is measured by the atomic force microscopy (AFM).