Ga and Al doped zinc oxide thin films for transparent conducting oxide applications: Structure-property correlations

摘要

We report a detailed investigation on the structure-property correlations in Ga and Al codoped ZnO films on c-sapphire substrates where the thin film microstructure varies from nanocrystalline to single crystal. We have achieved highly epitaxial films with very high optical transmittance (close to 90%) and low resistivity (～110 μΩ-cm) values. The films grown in an ambient oxygen partial pressure (P_(O2)) of 5 × 10~(-2) Torr and at growth temperatures from room temperature to 600 ℃ show semiconducting behavior, whereas samples grown at a P_(O2) of 1 × 10~(-3) Torr show metallic nature. The most striking feature is the occurrence of resistivity minima at relatively high temperatures around 110 K in films deposited at high temperatures. The measured optical and transport properties were found to be a strong function of growth conditions implying that the drastic changes are brought about essentially by native point defects. The structure-property correlations reveal that point defects play an important role in modifying the structural, optical, electrical, and magnetic properties and such changes in physical properties are controlled predominantly by the defect content.