Impact of cation compositions on the performance of thin-film transistors with amorphous indium gallium zinc oxide grown through atomic layer deposition

This paper reports the effect of the cation composition on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) where atomic layer deposition (ALD) was used to deposit an a-IGZO channel layer. The In 0.38 Ga 0.18 Zn 0.44 O transistors at a 200°C annealing temperature exhibited 39.4 cm 2 /V·s field effect mobility (µ FE ), −0.12 V threshold voltage (V TH ), 0.40 V/decade subthreshold gate swing (SS), and >10 7 I ON/OFF ratio, corresponding to the state-of-the-art characteristics of transistors with a sputtered IGZO channel. Further enhancement of the μ FE value was observed for the devices with a higher In fraction: the In 0.45 Ga 0.15 Zn 0.40 O transistor had a higher μ FE value of 48.3 cm 2 /V·s, −4.06 V V TH , 0.45 V/decade SS, and >10 7 I ON/OFF ratio. The cation composition dependence on the performance of the a-IGZO TFTs was explained by analysing the density-of-state (DOS) distribution for the corresponding devices using the experimental independent variable (IV) and theoretical Technology Computer-aided Design (TCAD) simulation.