Growth of c-axis oriented ZnO thin films with high deposition rate on silicon by CVD method

Abstract

A highly c-axis oriented ZnO thin film with a high optical transparency is grown at a high growth rate of 90μm/h on a silicon substrate by a ZnO-H₂-O₂-H₂O CVD system. Thin ZnO films are reproducibly obtained on silicon substrates only when an intermediately sputtered thin ZnO layer is present. In this CVD method, the intermediate thin ZnO layer provides a high density of nuclei and serves as a buffer layer in the succeeding CVD process. A ZnO film is selectively chemical-vapor-deposited on the part of the silicon substrate with a very thin sputter-deposited ZnO layer, with no chemical vapor deposition on the bare silicon substrate itself. The low resistivity, combined with optical transparency at visible to infrared, surface flatness, and good adherence to the silicon substrate of the ZnO film suggest the feasibility of ZnO/Si junction solar cells, which have shown a rather poor conversion efficiency of 0.92% so far.