Three-Dimensional Imaging of ELOG Growth Domains by Scanning Cathodoluminescence Tomography

Columnar ELOG growth domains formed in a 65 mm thick HVPE GaN layer during overgrowth of hexagonal SiO2 masks are three-dimensionally characterized using spatially and spectrally re-solved scanning cathodoluminescence (CL) microscopy. In conjunction with cross-sectional imaging perpendicular to the c-plane, a direct visualization of the 3D domain formation is achieved by con-secutive vertical series of CL mappings parallel to the c-plane. A perfect agreement between the local luminescence properties and the evolution of the local free carrier concentration during the different stages of overgrowth is confirmed by micro-Raman measurements. While mask-periodic domains with specific optical and electronic properties are observed for initial growth, homoge-neously high crystal quality at the sample surface is evidenced. Introduction Cathodoluminescence (CL) microscopy has proven its immense potential to characterize the evolution of the epitaxial lateral overgrowth of GaN (ELOG), evi-dencing the formation of specific growth domains with typical properties for a variety of mask patterns and growth conditions [1–4]. In these investigations, 2D imaging was performed either on cleaved faces perpendicular to the c-plane or on the as-grow