A comparative study of GaN epilayers grown on sapphire and SiC substrates by plasmahyphen;assisted molecularhyphen;beam epitaxy

摘要

We report structural, electrical, and optical data for GaN samples grown on both 6Hhyphen;SiC and sapphire substrates. A twohyphen;stage substrate preparation procedure was employed for removing oxygen from 6Hhyphen;SiC andchyphen;plane sapphire substrates without the need for elaborate highhyphen;temperature thermal degassing. Both sapphire and SiC substrates were treated with hydrogen plasma to reduce the surface contamination as evidenced by the observation of sharp (1times;1) reconstruction RHEED (reflected highhyphen;energy electrons diffraction) patterns. Thin AlN buffer layers were employed and the crystalline quality of GaN films was studied by temperaturehyphen;dependent Hall measurements, photoluminescence, and xhyphen;ray diffraction. Layers with roomhyphen;temperature mobilities as high as 580 cm2/Vthinsp;s on SiC substrates were obtained.