Controlling the resistivity gradient in chemical vapor deposition-deposited aluminum-doped zinc oxide

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 x 10(-4) Omega 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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747942