Deposition of GaN films on crystalline rare earth oxides by MOCVD

Abstract

Epitaxy of GaN films on crystalline rare earth oxide (cREO) buffer layers on Si(111) substrates was performed to explore the possibility of cREOs as a buffer layer for GaN-on-Si epitaxy. MOCVD GaN films were first deposited on Er2O3 and Gd2O3 layers with a MBE GaN capping layer to prevent reduction of the oxide in the H2 environment of an MOCVD reactor. This showed that a multi-layer stack of Er2O3 and Gd2O3 results in a higher quality GaN film than individual cREO layers with the rms roughness improvement of >1nm. MOCVD GaN films were also deposited on bare multilayer stacks of Er2O3 and Gd2O3 by first depositing a low temperature GaN layer grown without the presence of H2 at 700°C followed by a high temperature GaN film at 1030°C. This resulted in smooth films with rms roughness around 1nm and XRD rocking curve FWHM values of 1360″ for the (002) peak. For depositions on both GaN capped and bare oxides, nitridation of the oxides was found with XRD after the wafers went through the MOCVD process. This nitridation process could be impactful for the epitaxy of GaN-on-Si with cREOs by serving as a method of decoupling the epitaxial film from the mechanical constraints of the Si substrate.