Analytical Study of KOH Wet Etch Surface Passivation for III-Nitride Micropillars

TL;DR

This study investigates KOH wet etching for III-Nitride micropillars, demonstrating effective removal of etch damage and achieving smooth, vertical sidewalls suitable for high-performance optoelectronic devices.

Contribution

It provides a detailed analysis of KOH etching parameters, showing how to optimize surface passivation and sidewall quality in III-Nitride micropillars.

Findings

KOH preferentially etches <1-100> m-plane surfaces.

Optimal etching conditions produce RMS roughness as low as 2.59 nm.

Etch rate reaches up to 36.6 nm/min under specific conditions.

Abstract

III-Nitride micropillar structures show great promise for applications in micro light-emitting diodes and vertical power transistors due to their excellent scalability and outstanding electrical properties. Typically, III-Nitride micropillars are fabricated through a top-down approach using reactive ion etch which leads to roughened, non-vertical sidewalls that results in significant performance degradation. Thus, it is essential to remove this plasma etch induced surface damage. Here, we show that potassium hydroxide (KOH) acts as a crystallographic etchant for III-Nitride micropillars, preferentially exposing the vertical <1-100> m-plane, and effectively removing dry etch damage and reducing the structure diameter at up to 36.6 nm/min. Both KOH solution temperature and concentration have a dramatic effect on this wet etch progression. We found that a solution of 20% AZ400K (2% KOH) at 90 C is effective at producing smooth, highly vertical sidewalls with RMS surface roughness as low as 2.59 nm, ideal for high-performance electronic and optoelectronic devices.