Lithography-Free, Low-Cost Method for Improving Photodiode Performance   by Etching Silicon Nanocones as Antireflection Layer
  A three-step process has been demonstrated to improve the performance of photodiode by creating nanocone forest on the surface of photodiode as an antireflection layer. This high-throughput, low-cost process has been shown to decrease the reflectivity by 66.1%, enhance the quantum efficiency by 27%, and increase the responsivity by 25.7%. This low-cost manufacture process can be applied to increase the responsivity of silicon based photonic devices. 
Jing Jiang, Zhida Xu, Jiahao Lin, Gang Logan Liu
physics.ins-det physics.optics