Optical spectroscopy of GaN microcavities with thicknesses controlled using a plasma etchback

The effect of an etch-back step to control the cavity length within GaN-bas ed microcavities formed between two dielectric Bragg mirrors was investigat ed using photoluminescence and reflectivity. The structures are fabricated using a combination of a laser lift-off technique to separate epitaxial III -N layers from their sapphire substrates and electron-beam evaporation to d eposit silica/zirconia multilayer mirrors. The photoluminescence measuremen ts reveal cavity modes from both etched and nonetched microcavities. Simila r cavity finesses are measured for 2.0 and 0.8 mum GaN cavities fabricated from the same wafer, indicating that the etchback has had little effect on the microcavity quality. For InGaN quantum well samples the etchback is sho wn to allow controllable reduction of the cavity length. Two etch steps of 100 nm are demonstrated with an accuracy of approximately 5%. The etchback, achieved using inductively coupled plasma and wet chemical etching, allows removal of the low-quality GaN nucleation layer, control of the cavity len gth, and modification of the surface resulting from lift-off. (C) 2001 Amer ican Institute of Physics.