Semiconductor growth on porous substrates

We have studied different growth techniques for the deposition of compound semiconductors on highly structured and porous substrates. The idea behind these studies is the preparation of transparent spatially-distributed semiconductor heterojunctions. We used n-type nano- and microporous TiO2 films of several micrometers thickness as substrates, and CuI and CuSCN as the growing p-type semiconductors. CuI was deposited by electrodeposition of Cu on the TiO2 and subsequent iodation from the gas phase. Our results indicate that such two-step processes do not lend themselves to a complete filling of the porous structure. The second process studied uses a single-step electrodeposition process to deposit CuSCN from a solution of CuSCN+ complexes. Here the results indicate that a complete filling of the substrate void volume is easily achieved and a compact two-phase film with intimate contact between the two phases can be prepared. Under suitable conditions, the substrate can be filled to a degree of 100±3% with excellent, rectifying electrical contact between the growing material and the substrate.