(Invited) Top-Down Etching of III-Nitride Nanostructures

Abstract

Chemical etch processes for III-nitride (AlGaInN) materials and devices are significantly underdeveloped due to its apparent inertness to common wet etchants. To fully realize the potential of the III-nitrides in new electronic and photonic nano and micro device concepts, a more complete knowledge and development of anisotropic and three-dimensional top-down etch techniques are needed. Here, we explore the etch characteristics of GaN and AlGaN based materials using the general geometric principles of crystallographic dissolution processes to enable the prediction of facet-determined etch structures, including high aspect ratio nanowires and nanowalls. We perform the first complete nonpolar orientation-dependent etch rate measurements for GaN, and use them to predict the faceting of pillar structures with good agreement with experiment. We use these developments in wet etching to fabricate functional III-nitride-based optical nanowire and microcavity structures with control over the cross-sectional shape, where faceting enables sidewalls with near atomic-smoothness. Finally, we discuss a new fabrication method, quantum-size controlled photoelectrochemical etching, for the etching of InGaN quantum dots with high size uniformity from planar InGaN films.