Fabrication of three-dimensional GaAs antireflective structures by metal-assisted chemical etching

Antireflective GaAs subwavelength structures (SWSs) were fabricated by Au-assisted chemical etching. Thermally agglomerated Au nanoparticles caused catalytic reactions with the GaAs substrates in KMnO4 and HF etchant. Various features of the Au nanoparticles agglomerated after heat treatment of Au thin films. The reflectance of GaAs strongly depended on the three-dimensional features of the GaAs SWSs, which were controlled by Au agglomeration and chemical etching. GaAs SWSs dramatically reduced the total reflectance to 4.5% in a wavelength rage of 200-850 nm up to the incident angle of 50°. Solar-weighted total reflectance values quantitatively confirmed the highly efficient antireflective coating fabricated by metal assisted chemical etching on GaAs SWSs. To our knowledge, this is the first report that fabricates GaAs SWSs using metal-assisted chemical etching with thermally agglomerated metal catalyst. This technique is a viable alternative to conventional reactive ion etching and nano-lithography for fabricating antireflective SWSs for III-V solar cells.