MECHANISM OF PHOTOINDUCED CHARGE-TRANSFER OF CU-DOPED ZNO FILM IN STRONG ELECTRIC-FIELD

A three-layer film consisting of In-doped ZnO, Cu(Li)-doped ZnO and Au has been prepared by the sputtering method. Photocurrent measurements have been performed by applying a reverse bias to the In-doped ZnO an d Au electrodes. Continuous photocurrents are observed at wavelengths shorter than 780 nm, and a distinct peak is seen near 400 nm. Illumina tion with light of 365 nm during the photocurrent measurements results in an increase in photocurrent near 600 nm, but a decrease in photocu rrent near 700 and 400 nm. The mechanism of the photoinduced charge tr ansfer in the three-layer film is discussed on the basis of spectral a nd time dependence of photocurrent.