Cathodoluminescence Study of InP Photonic Structures Fabricated by Dry Etching

Ridge waveguides fabricated by inductively coupled plasma (ICP) etching using chlorine-based gases were studied by spectrum image cathodoluminescence (CL). Structures with different dimensions (height and width) were studied, evidencing the generation of defects during ICP processing. Using the CL spectrum images, the distribution of the stresses induced by the defects was mapped. The residual stresses depend on the dimensions of the waveguides. Using finite-element analysis the strain distribution was reproduced. The initial strain conditions provided a picture of the distribution of the defects generated by the etching process, showing differences between the etched floor, the side-walls of the waveguides, and the unetched top surface. The possible mechanisms for defect formation, as well as the possible identity of the defects, are discussed.