Low-resistive textured ZnO thin films grown by MOCVD and photo-MOCVD at very low-temperature of 150 degrees

Textured ZnO films were grown by metalorganic chemical vapor deposition (MOCVD) using diethylzinc (DEZ) and H₂O as reactant gases. For the low-substrate temperature of 150°C, the surface consists of uniformly sized tetrapod-like features. These undoped films have a high transparency in a wide wavelength range from 400 nm to 1400 nm. The B₂H₆ gas was also used as a n-type dopant gas to obtain highly conductive ZnO film with a resistivity of 2.4×10^-3 Ω-cm. Furthermore, the obtained ZnO films were used to fabricate an a-Si solar cell, and a high conversion efficiency of 11.2% was obtained. A novel photoexcitation process (photo-MOCVD) was employed for the improvement of the film quality, and it was found that the ultraviolet (UV) light irradiation onto the substrate during the growth was very effective in improving the electron mobility