Review Article: Atomic layer deposition of doped ZnO films

This article reviews the process-structure-property relationship in doped ZnO thin films via atomic layer deposition (ALD). ALD is an important manufacturing-scalable, layer-by-layer, thin film deposition process that precisely controls dopant type and concentration at the nanoscale. ZnO is an important technological material, which can be doped to modulate structure and composition to tailor a wide variety of optical and electronic properties. ALD doped ZnO is viewed as a transparent conducting oxide for application in solar cells, flexible transparent electronics, and light-emitting diodes. To date, there are 22 elements that have been reported as dopants in ZnO via ALD. This article studies the underlying trends across dopants and establishes generalized relationships for (1) the role of ALD process parameters, (2) the impact of these parameters on the structure of the ZnO matrix, and (3) the impact of dopants on the optical and electrical properties. The article ends with a brief discussion on the limitations of the ALD-based doping scheme, knowledge gaps in the compositional maps, and a perspective on the future of ALD doped ZnO films.