Solution-Processed Aluminum Oxide Phosphate Thin-Film Dielectrics

Aluminum oxide phosphate thin films have been deposited via spin coating from aqueous solution and utilized as gate dielectrics in thin-film transistors. Films are atomically smooth, dense, and amorphous, while exhibiting excellent morphological stability to 1000 °C. Film chemistry and structure are investigated by using an array of analytical techniques including X-ray diffraction, FT-IR spectroscopy, and electron-microprobe analysis. Dielectric film functionality and quality are explored through integration in capacitor and thin-film transistor devices. Film permittivity for an Al 2 PO 5.5 composition is found to be 4.8 in combination with leakage current densities <10 nA cm -2 at 1 MV cm -1 and current-limited breakdown fields up to 10 MV cm -1 . Thin-film transistors fabricated with these oxide phosphate dielectrics and sputtered ZnO channels exhibit strong field-effect and current saturation with incremental mobilities up to 3.5 cm 2 V -1 s -1 . The ability of the amorphous matrix to accommodate additional oxide components is demonstrated by the incorporation of La 2 O 3 and a resulting increase in film permittivity to 8.5, while maintaining breakdown fields >4 MV cm -1 .