Defects and mechanical stress during the dry etching of InP photonic structures: A cathodo-luminescence study

Introduction of point defects and mechanical stress during the dry etching process of InP-based photonic structures has been investigated using the spectroscopic cathodo-luminescence (CL) technique. The measurements were performed on cleaved cross-sections from standard passive waveguides with rectangular shape, different widths, etched in bulk InP using either reactive ion etching (RIE) with CH₄/H₂ as the etching gases, or high density - inductively coupled plasma (ICP) etching with SiCl₄. Point defects are created in the case of the ICP, SiCl₄-based process. The origin of these etching-induced defects is two-fold: formation at the interface between InP and the (non-stoichiometric) SiN_x etching mask layer, diffusion due to the temperature peak during the ICP etch process (heating induced by the high density ion bombardment specific for such processes). In addition to the formation of the point defects, dry etching processes were also observed to induce some mechanical stress in the passive photonic waveguides.