Strontium doping effects on the characteristics of solution-processed aluminum oxide dielectric layer and its application to low-voltage-operated indium-gallium-zinc-oxide thin-film transistors

Abstract In this paper, we investigated the strontium doping effects on the electrical and physical characteristics of solution-processed aluminum oxide dielectric layer and its application to low-voltage-operated indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs). With an optimized doping concentration of strontium (5 at%) in aluminum oxide (Al 2 O 3 ), an oxide gate dielectric layer having a dielectric constant of ~7 and low leakage current characteristics (~4 × 10 −7 A/cm 2 at 3 MV/cm) could be achieved by a solution process, which are comparably better than those of pristine Al 2 O 3 film. The enhanced dielectric properties from strontium doping can be attributed to the change in the physical properties of Al 2 O 3 film incorporated with strontium, providing charge relaxation of defect states in Al 2 O 3 film. Also, since the strontium is highly reactive with oxygen, the strontium substitution through a doping leads to more strongly bound structure in an Al 2 O 3 film without considerable lattice distortion. Using the strontium-doped aluminum oxide film as a gate dielectric layer, having a thickness less than 10 nm, solution-processed IGZO TFTs operating at ≤ 1 V were demonstrated showing a field-effect mobility of 1.74 ± 1.10 cm 2 /V s and an on-current level of ~10 −5 A.