The effects of vicinal sapphire substrates on the properties of AlGaN/GaN heterostructures

AlGaN/GaN heterostructures on vicinal sapphiresubstrates and just-oriented sapphire substrates (0001) are grown bythe metalorganic chemical vapor deposition method. Samples are studiedby high-resolution x-ray diffraction, atomic force microscopy,capacitance--voltage measurement and the Van der Pauw Hall-effecttechnique. The investigation reveals that better crystal quality andsurface morphology of the sample are obtained on the vicinal substrate.Furthermore, the electrical properties are also improved when the sampleis grown on the vicinal substrate. This is due to the fact that theuse of vicinal substrate can promote the step-flow mode ofcrystal growth, so many macro-steps are formed during crystalgrowth, which causes a reduction of threading dislocations in thecrystal and an improvement in the electrical properties of theAlGaN/GaN heterostructure.