Fabrication of periodically poled AlN with sub‐micron periods

Abstract

AbstractWe report on the fabrication of periodically poled AlN structures using inductive coupled plasma (ICP) etching and plasma‐assisted molecular beam epitaxy (PAMBE). Periodically poled AlN structures are fabricated by first depositing Al polar material on c‐plane sapphire substrates and then inverting the polarity through Mg overdoping. Subsequently, a grating with periods between 250 and 750 nm is defined by e‐beam lithography and etched into the film by inductive coupled plasma etching to expose stripes of Al‐polar material. ICP etching was optimized to produce vertical sidewalls and smooth Al‐polar regions. Finally, the patterned substrate is regrown by PAMBE to realize a periodically poled AlN structure. The sharpness of the interface between the Al and N polar regions is found to be dependent upon ICP etch conditions and III‐V flux during regrowth. Under III‐rich conditions, the alignment of the grating with crystallographic orientation has an important role in the final surface morphology. While lower III‐V flux ratios prevent faceting, regrowth of Al‐polar material is inhibited near the sidewalls of trenches with high aspect ratios. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)