Methods of metal assisted chemical etching III-V semiconductors are provided. The methods can include providing an electrically conductive film pattern disposed on a semiconductor substrate comprising a III-V semiconductor. At least a portion of the III-V semiconductor immediately below the conductive film pattern may be selectively removed by immersing the electrically conductive film pattern and the semiconductor substrate into an etchant solution comprising an acid and an oxidizing agent having an oxidation potential less than an oxidation potential of hydrogen peroxide. Such methods can form high aspect ratio semiconductor nanostructures.