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 degrees 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 Al2PO5.5 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 La2O3 and a resulting increase in film permittivity to 8.5, while maintaining breakdown fields > 4 MV cm(-1).