“…Top-down and bottom-up methods are two approaches used to produce GaAs nanostructures by a variety of physical [7, 8], chemical [9], and electrochemical etching techniques [10]. GaAs nanostructures can be obtained in different forms and shapes including quantum wells [11], nanowires [12], quantum dots (QDs) [13], quantum dot molecules [14], quantum rings (QRs) [15], nanodiscs [16], coupled ring/disks [17], nanopillars [18], nanoholes [19], and nanopores [20]. Electrochemically formed porous GaAs nanostructures are particularly attractive for many applications due to their unique nanoscale properties and high surface-to-volume ratio.…”