Controlling the physical and electrical properties of ALD grown ZnO using Nb as a dopant

Thin-film transistors (TFTs) have been fabricated using atomic layer deposition (ALD) Nb-doped ZnO (Nb:ZnO) for the active layer. The optical and electrical properties of the Nb:ZnO TFTs for Nb cycle percentage between 0 and 12.5 % were studied. The optical band gap is seen to increase with Nb content, where a cycle percentage of 12.5% gives an increase of 0.27 eV to 3.54 eV. The device with 3.8% Nb:ZnO exhibited the best TFT characteristics, with an On/Off ratio of 10
⁸
, saturation mobility of 5.1 cm
²
/Vs, threshold voltage of 5.1 V and sub-threshold swing of 0.51 V/dec. The characteristic temperature of the material, derived from a model based on an exponential density of states, indicates that the disorder within the material is reduced compared to the use of Mg doping.