Insight about electrical properties of low-temperature solution-processed Al-doped ZnO nanoparticle based layers for TFT applications

- Al-doped ZnO (AZO) nanoparticles.
- Impact of dispersion state and solid state on electrical properties.
- Extrinsic doping with Al for high conducting AZO nanoparticle based layers.
- Low-temperature operating nanoparticulate AZO TFTs.

Aluminium-doped zinc oxide nanoparticles (NPs) with controlled Al doping contents (AZOx with x = 0-0.8 at% of Al) were explored as new oxide semiconductor materials to study the impact of doping on both solution and solid states. Polycrystalline AZOx thin films were produced by spin-coating the dispersions following by a thermal post-treatment at low-temperature (80 °C or 150 °C). The coated AZOx films were employed as active layer in thin-film transistors. Morphology and microstructure were studied by scanning electron microscopy and X-ray diffraction. The impact on the device performances (mobility, conductivity, charge carrier density) of Al-doping content together with the solution state was examined. Spin-coated films delivered an electron mobility up to 3 × 10−2 cm2/Vs for the highest Al-doping ratio AZO0.8. Despite highly different morphologies, extrinsic doping with aluminium significantly increases the conductivity of low temperature solution-processed AZOx NPs series based layers by several orders of magnitude from AZO0 to AZO0.8.