Growth and characterization of AlGaN/GaN heterostructure using unintentionally doped AlN/GaN superlattices as barrier layer

AlGaN/GaN heterostructure using unintentionally doped AlN/GaN superlattices (SLs) as barrier layer is grown on C-plane sapphire by metal organic vapor deposition (MOCVD). Compared with the conventional Si-doped structure, electrical property is improved. An average sheet resistance of 287.1Ω/□ and high resistance uniformity of 0.82% are obtained across the 2-inch epilayer wafer with an equivalent Al composition of 38%. Hall measurement shows that the mobility of two-dimensional electron gas (2DEG) is 1852 cm2/V s with a sheet carrier density of 1.2×1013 cm−2 at room temperature. The root mean square roughness (RMS) value is 0.159 nm with 5×5 μm2 scan area and the monolayer steps are clearly observed. The reason for the property improvement is discussed.