Limiting factors of carrier concentration and transport of polycrystalline Ga-doped ZnO films deposited by ion plating with dc arc discharge

Abstract

We develop a deposition technology to enhance carrier concentration (N) together with the improvement of carrier transport of transparent conductive Ga-doped ZnO (GZO) polycrystalline films. 200-nm-thick GZO films were deposited on glass substrates at a temperature of 200°C by ion plating with dc arc discharge. We investigated the effects of oxygen (O2) gas flow rates (OFRs) and discharge current (ID) added between the plasma gun and resource pellet on structural and electrical properties of GZO films. The Ga2O3 contents in the resource pellets was 4.0wt.%. During film growth, O2 gas was introduced into the deposition chamber to control point defects. We found that OFR is the main limiting factor of N and the contribution of grain boundaries (GBs) scattering to carrier transport, whereas ID limits the carrier transport in grain bulk. By optimizing OFRs and ID to obtain high N and Hall mobility (μH) limited by intragrain scattering, we achieved GZO films with an electrical resistivity value of 1.96×10−4Ωcm, an N value of 1.25×1021cm−3 and a μH value of 25.4cm2/Vs.