Comparison of growth methods for Si/SiO2 nanostructures as nanodot hetero-emitters for photovoltaic applications

Two different growth mechanisms are compared for the fabrication of Si/SiO2 nanostructures on crystalline silicon (c-Si) to be used as hetero-emitter in high-efficiency solar cells: (1) The decomposition of substoichiometric amorphous SiOx (a-SiOx) films with 0 < x < 1.3 and (2) the dewetting of thin amorphous silicon (a-Si) layers.The grown layers are investigated with regard to their structural properties, their passivation quality for c-Si wafer substrates and their electrical properties in order to evaluate their suitability as a nanodot hetero-emitter. While by layer decomposition, no passivating nanodots could be formed, the dewetting process allows fabricating nanodot passivation layers at temperatures as low as 600 °C. The series resistance through Ag/[Si-nanodots in SiO2]/c-Si/Al structures for dewetting is similar to nanostructured silicon rich SiOx films. Still, a nanodot hetero-emitter which exhibits both a satisfying passivation of the substrate and induces a high band bending by doping at the same time could not be fabricated yet.

► We compare two growth mechanisms for the fabrication of Si/SiO2 nanostructures. ► Growth mechanisms are dewetting of SiOx and decomposition of amorphous silicon. ► We compare the structure, passivation and conductivity of the nanostructures. ► No passivation for decomposition, high band bending by doping. ► No dewetting for doped layers, temperature stable passivation.