Broadband perfect metamaterial absorber based on the gallium arsenide grating complex structure

We propose a broadband metamaterial absorber consisting of a periodic gallium arsenide (GaAs) grating array standing on a tungsten (W) film separated by an ultra-thin GaAs spacer layer. A perfect absorption broadband is achieved with an average absorption of 97% in the range from 506 nm to 1814 nm. The bandwidth with the absorption over 90% is larger than 1300 nm and the maximum absorption is up to 100%. The broadband perfect absorption results from the excited surface plasmons combined with the cavity modes. High short-circuit current density over 56 mA/cm(2) and near-unity solar energy trapping are also obtained using this absorber due to the multiple resonances coupling. Moreover, this absorber requires no noble metal and is compatible with the popular nano-fabrication technologies. These offer new perspectives for achieving thin film solar cells, solar energy harvesting, magnetic recording, ultra-thin and durable optoelectronic elements.