Wet-based digital etching on GaN and AlGaN.

Many advanced III-nitride devices, such as micro-LEDs, vertical FinFETs, and field emitters, require the fabrication of high aspect ratio vertical pillars or nanowires. Two-step etchings combining dry and wet etching steps have been used on vertical devices in the past, but they show poor control in vertical nanostructures with sub-50 nm diameter. In this work, we demonstrate a wet-chemical digital etching on GaN and AlGaN and apply it to both vertical nanostructure scaling and planar etching along the c-axis. In this digital etching process, a mixture of H2SO4 and H2O2 is applied to oxidize the III-nitrides surface, and the oxide layer is then removed by dilute HCl. This digital etching approach can finely sharpen vertical structures and does not require any vacuum or plasma systems, which will enable advanced device structures in the future. [ABSTRACT FROM AUTHOR]