Growth condition optimization and mobility enhancement through prolonging the GaN nuclei coalescence process of AlGaN/AlN/GaN structure

AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas（2DEG） performance are investigated. Lowering the V/III ratio and enhancing the reactor pressure at the initial stage of the hightemperature GaN layer growth will prolong the GaN nuclei coalescence process and effectively improve the crystalline quality and the interface morphology, diminishing the interface roughness scattering and improving 2DEG mobility. AlGaN/AlN/GaN structure with 2DEG sheet density of 1.19 × 10^13cm^-2, electron mobility of 2101 cm^2·V^-1·s^-1, and square resistance of 249 Ω is obtained.