A team of University of Illinois researchers. developed a method to chemically etch high aspect ratio patterned arrays in gallium arsenide, which is used in numerous optoelectronic components. Electrical and computer engineering professor, Xiuling Li, led the researchers in the development which they describe in the journal Nano Letters.
Li and her group turned to metal assisted chemical etching ( MacEtch), a wet-etching approach, which Li says is faster and less expensive than many dry etch methods but can produce high aspect ratio structures that could previously only be produced with dry etch. The group previously developed MacEtch for use with silicon. Li’s group optimized the chemical solution and reaction conditions for the III-V semiconductor gallium arsenide (GaAs).
First, the researchers used professor John Roger’s “soft lithoagraphy” method to pattern a thin film on the GaAs surface without expensive optical equipment. Then, the semiconductor with the metal pattern is immersed in the MacEtch chemical solution. The metal catalyzes the reaction so that only the areas touching metal are etched away, and high-aspect-ratio structures are formed as the metal sinks into the wafer. When the etching is done, the metal can be cleaned from the surface without damaging it.