Roles for aluminium indium nitride insertion layers in fabrication of GaN-based microcavities

AlInN alloys achieve an in-plane lattice match to hexagonal GaN at an indium nitride mole fraction of 18%. Meanwhile Al0.82In0.18N displays a refractive index contrast of 7% with GaN at visible wavelengths. We illustrate the use of Al0.82In0.18N insertion layers to control layer thicknesses during homoepitaxial growth of GaN-based microcavities, using in situ optical reflectometry. The structures discussed are 3 /2 microcavities incorporating distributed InGaN quantum wells tailored for emission at 400 nm. As-grown samples have been characterised by techniques including cathodoluminescence spectroscopy. In addition to their role in growth monitoring, there are several post-growth processing steps in which Al0.82In0.18N insertion layers can assist microcavity fabrication. We focus here on a demonstration of the 1:5 etch rate selectivity obtainable between Al0.82In0.18</SUB >N and GaN in reactive ion etching