Effects of formation of mini-bands in two-dimensional array of silicon nanodisks with SiC interlayer for quantum dot solar cells
Makoto Igarashi1,2, Mohd Fairuz Budiman1, Wugen Pan3, Wei
guo Hu1,2, Yosuke Tamura1,2, Mohd Erman Syazwan1,2, Noritaka Usami3 and Seiji Samukawa1,2,4
A sub-10 nm, high-density, periodic silicon nanodisk (Si-ND) array with a SiC interlayer has been fabricated using a new top-down process that involves a 2D array of a bio-template etching mask and damage-free neutral beam etching. Optical and electrical measurements were carried out to clarify the formation of mini-bands due to wavefunction coupling. We found that the SiC interlayer could enhance the optical absorption coefficient in the layer of Si-NDs due to the stronger coupling of wavefunctions. Theoretical simulation also indicated that wavefunction coupling was effectively enhanced in Si-NDs with a SiC interlayer, which precisely matched the experimental results. Furthermore, the I–V properties of a 2D array of Si-NDs with a SiC interlayer were studied through conductive AFM measurements, which indicated conductivity in the structure was enhanced by strong lateral electronic coupling between neighboring Si-NDs. We confirmed carrier generation and less current degradation in the structure due to high photon absorption and conductivity by inserting the Si-NDs into p–i–n solar cells.