Highly stable non-polar p-type Ag-doped ZnO thin films grown on r-cut sapphire

Non-polar p-type Ag-doped ZnO thin films were grown on r-cut sapphire substrates by pulsed laser deposition. Films deposited at a substrate temperature above 250 °C were shown to be (112¯0) oriented (a-plane) according to X-ray diffraction, and maintained p-type behavior after one year according to Hall-effect measurements. Hole carrier concentrations lie in the range of 3.1×1016–5.3×1017 cm−3, mobilities in the range of 0.3–1.5 cm2 V−1 s−1, and resistivities in the range of 43–136Ωcm. Optical transmittance measurements indicate a decrease in band gap of ∼0.07–0.08eV for the p-type films. Characteristic stacking fault features were observed along the (011¯2) plane in the p-type films by transmission electron microscopy.

► Non-polar (a-plane) p-type Ag-doped ZnO thin films were grown under optimized deposition conditions on r-cut sapphire substrates using pulsed laser deposition. ► Hall measurements indicate that films deposited at temperatures greater than 250 °C were stable in their p-type conductivity after 1 year. ► Characteristic stacking fault features were in the p-type films by transmission electron microscopy. ► We report on the possible route for achieving stable, high-quality, non-polar p-type ZnO films, which is desirable for non-polar ZnO based optoelectronic devices.