Thermally driven metal-assisted chemical etching of GaAs with in-position and out-of-position catalyst

We have identified the characteristic stages of metal-assisted chemical etching of GaAs. Distinct changes in the surface topologies were classified into etching at incubation, out-of-position, and in-position of the metal catalyst. Thermally activated chemical etching and mass transport influence the catalytic reactions of electronic holes, oxidation of GaAs, and subsequent removal of porous GaAs. At low temperatures with a slow etch rate, only porous regions encircling the metal catalyst were etched on the GaAs. At mid temperatures, chemical etch occurred substantially out-of-position of the Au catalyst, forming arrays of craters on GaAs. At high temperatures, etching occurred in-position of the Au catalyst with an array of bumps on the GaAs. After a prolonged etch, high aspect ratio pillars were fabricated with a high vertical etch rate and the pillar diameters were shrunk to nano-scale with a controlled lateral etch. Three distinct stages that consecutively evolved during metal-assisted chemical etching of GaAs were determined to be caused by thermally driven electronic holes and chemical reactions.