Mosaic Defects of AlN Buffer Layers in GaN/AlN/4H-SiC Epitaxial Structure

Abstract

Structural properties of AlN buffer layers, grown by Metal Organic Chemical Vapor Deposition (MOCVD) on 4H-SiC substrate with thicknesses of 61.34, 116.88, 129.46 and 131.50 nm, are investigated by High Resolution X-Ray Diffraction (HR-XRD) technique. Interfacial roughness of AlN buffer layer was determined by XRR technique. The interface roughness value of 131.50 nm thick sample is determined as 0.50 nm. Mosaic defects, tilt angle, vertical and lateral coherence lengths are characterized by HR-XRD technique. The edge and screw dislocations of the 131.50 nm thick sample are found as 2.98x1010 and 8.86x108 cm-2 respectively. The results indicate that 131.50 nm thick AlN buffer layer should be used in order to gain high performance in optoelectronic terms in this study. Thus, optimization of AlN buffer layer thickness is extremely important in device performance.