P-type electrical conduction in transparent thin films of CuAlO2
Abstract
Optically transparent oxides tend to be electrical insulators, by virtue of their large electronic bandgap (>=3.1eV). The most notable exceptions are doped versions of the oxides In2O3, SnO2 and ZnO-all n-type (electron) conductors-which are widely used as the transparent electrodes in flat-panel displays. On the other hand, no transparent oxide exhibiting high p-type (hole) conductivity is known to exist, whereas such materials could open the way to a range of novel applications. For example, a combination of the two types of transparent conductor in the form of a pn junction could lead to a `functional' window that transmits visible light yet generates electricity in response to the absorption of ultraviolet photons. Here we describe a strategy for identifying oxide materials that should combine p-type conductivity with good optical transparency. We illustrate the potential of this approach by reporting the properties of thin films of CuAlO2, a transparent oxide having room-temperature p-type conductivity up to 1Scm-1. Although the conductivity of our candidate material is significantly lower than that observed for the best n-type conducting oxides, it is sufficient for some applications, and demonstrates that the development of transparent p-type conductors is not an insurmountable goal.
- Publication:
-
Nature
- Pub Date:
- October 1997
- DOI:
- 10.1038/40087
- Bibcode:
- 1997Natur.389..939K