Metalorganic Chemical Vapor Deposition of GaN and InGaN on ZnO Substrate using Al_2O_3 as a Transition Layer

摘要

Al_2O_3 films were deposited on the Zn face of ZnO (0001) substrates as a transition layer by atomic layer deposition (ALD). The as-deposited 20 and 50nm Al_2O_3 films were transformed to polycrystalline a-Al_2O_3 phase after optimal annealing at 1100°C after 10 and 20 minutes, respectively, as identified by high resolution x-ray diffraction (HRXRD). Furthermore, GaN and InGaN layers were grown on annealed 20 and 50nm Al_2O_3 deposited ZnO substrates by metalorganic chemical vapor deposition (MOCVD) using NH_3 as a nitrogen source at high growth temperature. Wurtzite GaN was only seen on the 20nm Al_2O_3/ZnO substrates. Room temperature photoluminescence (RT-PL) shows the near band-edge emission of GaN red-shifted, which might be from oxygen incorporation forming a shallow donor-related level in GaN. Raman scattering also indicated the presence of a well-crystallized GaN layer on the 20nm Al_2O_3/ZnO substrate. InGaN was grown on bare ZnO as well as Al_2O_3 deposited ZnO substrates. HRXRD measurements revealed that the thin Al_2O_3 layer after annealing was an effective transition layer for the InGaN films grown epitaxially on ZnO substrates. Auger Electron Spectroscopy (AES) atomic depth profile shows a decrease in Zn in the InGaN layer. Moreover, (0002) InGaN layers were successfully grown on 20nm Al_2O_3/ZnO substrates after 10min annealing in a high temperature furnace.