Fabrication of uniform, periodic arrays of exotic AlN nanoholes by combining dry etching and hot selective wet etching, accessing geometries unrealisable from wet etching of planar AlN

Aluminium nitride (AlN) is a wide bandgap semiconductor with far reaching realised and potential applications in electronics and optoelectronic technology. For example, gallium nitride (GaN) quantum dots (QDs) housed within an AlN matrix are attractive due to the large bandgap offsets. However, making suitable AlN sites to house GaN QDs is challenging due to the difficulty in fashioning 3D AlN structures. This results from AlN's strong bonds that are difficult to chemically etch. Whilst dry etching of AlN nanostructures has been explored, wet etching at the nanoscale has been limited by the common exposed facet of AlN being etch-resistant. Hence, wet etching of AlN to create uniform arrays of periodic nanohole nanostructures has, thus far, not been heavily explored. In this paper, an initial dry etching of a 2D AlN planar template is used to expose alternative wet-etchable facets so that periodic arrays of nanohole structures are revealed by wet-etching. Both a study of different initial dry etched structures, including tapered nanoholes, and wet etching time were performed. A model to describe the dynamics of wet etching on the different dry etched nanohole structures is proposed. Periodic arrays of uniform nanohole features are realised that hold promise for applications such as the housing of site-controlled quantum dots. • Faceted nanohole structures. • Tapered nanoholes. • Combined dry and wet etching. • Exotic inclined planes.