Anisotropy and Mechanistic Elucidation of Wet‐Chemical Gallium Nitride Etching at the Atomic Level. Issue 21 (10th September 2020)

• Record Type: Journal Article
• Authors: Tautz, Markus; Weimar, Andreas; Graßl, Christian; Welzel, Martin; Díaz Díaz, David
• Is Part Of: Physica status solidi. Volume 217:Issue 21(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-10
• Subjects: anisotropy -- etching -- gallium nitride -- light-emitting diodes -- mechanism; Solid state physics -- Periodicals; Solids -- Industrial applications -- Periodicals; 530.41
• DOI: 10.1002/pssa.202000221
• Languages: English
• ISSNs: 1862-6300

Abstract

Abstract : Etching of gallium nitride is a key step in the production of blue and white light‐emitting diodes (LEDs). Etching in aqueous KOH solution creates a rough surface on the LED chip to facilitate outcoupling of the photons generated, drastically increasing the resulting LED's efficiency. Compared with the common technique of dry etching, wet‐chemical etching using aqueous KOH solution has significant advantages, e.g., lower complexity and cost and less remaining surface damage. An in‐depth analysis of the molecular etch reaction by characterization of the reaction products is reported. The mechanism identified explains the cause of anisotropic etching, which leads to the formation of hexagonal pyramids. The concept of hydroxide repulsion by protruding NH and NH2 groups established in the literature is adapted and further developed. The susceptibility of several polar, semipolar, and nonpolar crystal facets may also be explained, as well as the commonly observed increase in average pyramid size over etch time. Abstract : Gallium nitride is the key material of blue and white light‐emitting diodes. Its etch behavior in alkaline solution has been debated for 30 years. This study elucidates the molecular reaction mechanism occurring during etching. The established concept of hydroxide repulsion by surface‐standing NH and NH2 groups is extended to explain the etch behaviors of the most important crystal facets.