Photovoltaic effect in a structure based on amorphous and nanoporous silicon formed by plasma immersion ion implantation

A p-i-n structure with photovoltaic properties was proposed and fabricated by plasma immersion ion implantation. Implantation of helium ions with an energy of 1 to 5 keV with subsequent annealing creates a region of nanoporous silicon at a depth of ～20 to 80 nm from the silicon substrate surface. A nanocrystalline structure of this layer results in high light absorption and a change in the band-gap energy, which leads to the formation of a heterojunction. The upper layer of the modified region was additionally doped with boron to create a p region. The resulting structure showed a photovoltaic effect (0.15 V, 6.4 mA/cm²) under illumination with light equivalent to sunlight in terms of the spectral range and intensity.