Role of gallium and yttrium dopants on the stability and performance of solution processed indium oxide thin-film transistors

Abstract

We study the effect of gallium and yttrium doping on both the electrical performance and the stability of indium based metal-oxide thin-film transistors (MOTFTs) at varied concentrations. As the Ga (Y) content in the In_1.0Ga_xO_y (In_1.0Y_xO_y) channel material was increased to x = 0.1 the mobility of the MOTFTs degrades by a factor of 4. Thereby the temperature stress stability is clearly enhanced by increasing doping concentration: the onset voltage shift is reduced by a factor of 3 for both In_1.0Ga_0.1O_y and In_1.0Y_0.1O_y films compared to that in indium-oxide TFTs. Also the stability during negative bias stress (NBS) is improved since the strong oxygen binders Ga and Y prevent the desorption of oxygen at the surface. In contrast, the onset voltage shift during positive bias stress (PBS) of doped metal oxide TFTs is higher ΔV_on = 12 V for InGaO (100 : 10) TFTs and ΔV_on = 15 V for InYO ((100 : 10) TFTs) compared to that of intrinsic indium oxide TFTs (ΔV_on = 6 V), which could be attributed to the generation of flat trap states at the dielectric/semiconductor interface. Doping with Ga and Y significantly enhances the temperature and NBS stability of TFTs and simultaneously degrades the performance.