InGaN/GaN mesas variability studied by Dark Field X-ray Microscopy

For the development of efficient µdisplays, CEA-Leti is developing a new “InGaN” substrate. This new substrate is made of a 200 nm InGaN layer which is patterned into few µm mesas. The patterning allows strain relaxation of the InGaN layer, which is the main goal of this substrate. Previous cathodoluminescence measurements and scanning x-ray diffraction measurements showed surprisingly large variability in behaviour from mesa to mesa. We believe that this variability may be related to structural inhomogeneity (domain tilt, strains, structural defects such as dislocations, etc.). Our objective in this study is to image a large number of mesas in diffraction mode in order to determine the origin of this variability by relating it to cathodoluminescence measurements.