Diffused Oxygen as Dominating Shallow Acceptor in p-Type Copper Iodide Thin Films

The long-term stability of the optically transparent p-type semiconductor copper iodide is a current challenge. The electrical conductivity of CuI thin films depends critically on the environmental impact. Al2O3 cappings enhance the stability considerably. Systematic studies on Al2O3/CuI heterostructures in dependence of the N-2/O-2 growth pressure show the electrical conductivity of the CuI films being determined by the oxygen diffusion through Al2O3 und CuI. Oxygen seems to be a dominating acceptor in CuI. We traced the diffusion of atmospheric oxygen into CuI with O-18 isotopes.