Controlling the resistivity gradient in aluminum-doped zinc oxide grown by plasma-enhanced chemical vapor deposition

Aluminum-doped ZnO (ZnO:Al) grown by chemical vapor deposition (CVD) generally exhibit a major drawback, i.e., a gradient in resistivity extending over a large range of film thickness. The present contribution addresses the plasma-enhanced CVD deposition of ZnO:Al layers by focusing on the control of the resistivity gradient and providing the solution towards thin (=300¿nm) ZnO:Al layers, exhibiting a resistivity value as low as 4¿×¿10-4 O cm. The approach chosen in this work is to enable the development of several ZnO:Al crystal orientations at the initial stages of the CVD-growth, which allow the formation of a densely packed structure exhibiting a grain size of 60–80¿nm for a film thickness of 95¿nm. By providing an insight into the growth of ZnO:Al layers, the present study allows exploring their application into several solar cell technologies