ZnCdO: Status after 20 years of research

With the increasing attention devoted to ZnO in the late nineties, the discovery of ZnCdO as a means of reducing its bandgap towards visible wavelengths promised it a bright future in optoelectronics, which should run in parallel to its possible applications as a transparent conducting oxide. This review will cover the developments achieved so far in the growth of ZnCdO, in the understanding of its structural properties, paying special attention to the competition between wurtzite and rocksalt phases, as well as in the analysis of its optical and electronic properties. Finally, some of the devices demonstrated with ZnCdO will be reviewed together with the difficulties they have encountered.