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

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 (Al2O3), an oxide gate dielectric layer having a dielectric constant of ~7 and low leakage current characteristics (~4 × 10−7 A/cm2 at 3 MV/cm) could be achieved by a solution process, which are comparably better than those of pristine Al2O3 film. The enhanced dielectric properties from strontium doping can be attributed to the change in the physical properties of Al2O3 film incorporated with strontium, providing charge relaxation of defect states in Al2O3 film. Also, since the strontium is highly reactive with oxygen, the strontium substitution through a doping leads to more strongly bound structure in an Al2O3 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 cm2/V s and an on-current level of ~10−5 A.