Homoepitaxial HVPE GaN: A potential substrate for high performance devices

•Thick freestanding HVPE-GaN with very low dislocation density.•Biaxial stress free substrate for homoepitaxy growth.•Probing uniform areal and volumetric distribution of pervasive impurities.•Identification of intrinsic pervasive donor and acceptor impurities.•High free carrier mobility. We investigated the structural, optical, and electrical properties of thick freestanding HVPE GaN films deposited on and then removed from substrates consisting of thick HVPE-GaN deposited on ammonothemal-substrates. High-resolution XR diffraction of both Ga- and N-polar faces and XR topography studies confirmed high crystalline quality. Raman scattering measurements carried on both polar faces of these samples confirm that they are free of biaxial stress, and also confirm that the Si concentration increases with growth, as verified by SIMS analysis. This variation in the incorporation of the Si shallow impurity was also observed in the photoluminescence of these samples. Electrical transport measurements are consistent with good electrical properties. The results strongly suggest that this type of substrate could be conveniently tailored for the fabrication of high performance devices.