Facet formation for laser diodes on nonpolar and semipolar GaN

Abstract

AbstractDifferent technologies have been evaluated in order to create vertical and smooth facets for GaN‐based laser diodes on non‐ and semipolar substrates. Laser assisted scribing and cleaving proved to be a suitable method to create c‐, a‐ and m‐plane facets for devices grown on nonpolar, polar and semipolar GaN planes. The RMS roughness measured by atomic force microscopy was found to be less than 1 nm. Semipolar facets showed tilted or multifaceted cleavage planes. Dry etching using inductively coupled plasma etching (ICP) resulted in vertical facets for devices grown on polar c‐plane GaN, while the facets of semipolar $(11\overline 2 2)$ GaN on sapphire exhibited a slight tilt depending on the crystal orientation. Wet chemical postprocessing of semipolar facets can improve the tilt angle but suffers from a roughening of the facets due to selective dislocation etching. By using a focussed ion beam (FIB) it is possible to create vertical and smooth facets independent of the crystal orientation.