The effect of substrate temperature on high quality c-axis oriented AZO thin films prepared by DC reactive magnetron sputtering for photoelectric device applications

Abstract

In this paper, in order to find the optimal condition for fabricating photoelectric devices, we investigated Al doped ZnO (AZO) thin films on glass substrates were deposited by DC reactive magnetron sputtering using Zn/Al alloy target. The structural, electrical and optical properties of the AZO films prepared at various substrate temperatures were investigated. The results indicate each of the films has a preferential c-axis orientation and the grain size increases with substrate temperature increasing. As the substrate temperature was higher, the resistivity of AZO films was greatly decreased due to an increase in carrier concentration and mobility. The high c-axis oriented AZO film possesses high quality in terms of electrode functions at the substrate temperature of 480°C. The resistivity is as low as 4.973×10−4Ωcm, the carrier concentration and mobility are as high as 1.103×1021atom/cm3 and 11.4cm2/Vs, respectively. We find that both substitutional Al and oxygen vacancies contribute to the donor generation from XPS spectra. The average transmittance of the film is about 90% in the visible region. We can see that under reverse bias conditions the photocurrent of novel AZO/p-Si heterojunction, which prepared by DC reactive magnetron sputtering at 480°C substrate temperature, is much higher than the photocurrent of the AZO/p-Si heterojunction prepared by DC magnetron sputtering. Because the high quality crystallite and the good conductivity of AZO film prepared by DC reactive magnetron sputtering leads to a great decrease of the lateral resistance. The photon induced current can easily flow through top film entering the Cu front contact. Thus, high photocurrent is obtained under a reverse bias.