Top-down fabricated tapered GaAs nanowires with sacrificial etching of the mask

A novel fabrication method using controlled sacrificial etching of the mask is utilized to fabricate tapered vertical GaAs nanowire arrays. Experimental measurements of the absorption characteristics show that the tapered nanowires absorb over a broadband range as compared to cylindrical ones. The broadband characterization is verified by using optical modeling and results from improved coupling of the nanowires due to distinct radial HE modes being excited separately in the taper and the cylindrical part. The absorption is found to be more broadband as compared to conical nanowires studied so far.