INFLUENCE OF DEPOSITION PARAMETERS ON ELEMENTAL CONCENTRATIONS, ELECTRICAL, AND OPTICAL PROPERTIES OF MAGNETRON CO-SPUTTERED AL-DOPED ZNO FILMS

摘要

We investigate the influence of various deposition parameters on Zn and Al elemental concentrations in relation to their effect on the optical and electrical properties of co-sputtered Al-doped zinc oxide (ZnO:Al) films. To determine the Al and Zn concentrations Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) is applied. It is shown, that the Al doping concentration c_(Al) strongly depends on the deposition parameters and has a strong influence on the charge carrier density of the films. High Al concentrations of 6.4·10~(20) and 8.5·10~(20) cm~(-3) are obtained at increased sputtering temperature (450°C) and reduced oxygen flow (6 sccm), respectively, allowing charge carrier densities N_e up to 2.2·10~(20)cm~(-3) and electrical resistivities below 2.0·10~(-3) Ωcm. However, as opposed to an increased sputtering temperature, a low oxygen flow significantly reduces the film transparency. The working pressure appears to have a less profound impact on the Al concentration, but more on the charge carrier mobility and defect density within the films: an increase from 0 5 to 1.5 mTorr decreases the ratio N_e/c_(Al), which is a measure for the defect density, by a factor of seven and simultaneously leads to a decrease of mobility from 29 to 2 cm~2V~(-1)s~(-1). XRD measurements indicate, that higher working pressure leads to poorer crystallinity.