Wet-chemical nanoscale patterning of GaAs surfaces using atomic force microscope lithography

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Sub-100 nm V-grooves in GaAs(001) surfaces have been fabricated by patterning a thin photoresist layer with an atomic force microscope (AFM) and subsequent wet-chemical etching. The nanolithography is based on the dynamic ploughing technique. Anisotropic etchants under investigation are bromine–methanol–isopropanol, sulfuric acid–hydrogen peroxide–water, citric acid–hydrogen peroxide–water, and ammonium hydroxide–hydrogen peroxide–water. Along the [11̄0] direction the etched grooves are V-shaped, along [11̄0] the profile is U-shaped. Best results of 50–60-nm wide V-grooves with straight edges and smooth sidewalls are obtained from bromine–methanol–isopropanol, the other etchants form rough grooves. Concerning the reproducibility of the patterning process, the aqueous etch solutions exceed the bromine etchant.