Abstract
ABSTRACTThis 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 In0.38Ga0.18Zn0.44O transistors at a 200°C annealing temperature exhibited 39.4 cm2/V·s field effect mobility (µFE), −0.12 V threshold voltage (VTH), 0.40 V/decade subthreshold gate swing (SS), and >107 ION/OFF ratio, corresponding to the state-of-the-art characteristics of transistors with a sputtered IGZO channel. Further enhancement of the μFE value was observed for the devices with a higher In fraction: the In0.45Ga0.15Zn0.40O transistor had a higher μFE value of 48.3 cm2/V·s, −4.06 V VTH, 0.45 V/decade SS, and >107 ION/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.
Highlights
The demand for thin-film transistors (TFTs) with high performance has been increasing due to the need for low power consumption, ultra-high pixel density, good form factor, and interactive functionality
The cation-composition-dependent performances of the amorphous indium gallium zinc oxide (a-indium gallium zinc oxide (IGZO)) TFTs were explained by analyzing the distribution of the density of states (DOS) in a band gap, which were extracted by measuring the temperature-dependent independent variable (IV) characteristics based on the Meyer-Neldel rule (MN rule)
A linear relationship was observed between the number of atomic layer deposition (ALD) cycles and the film thickness, which is expected in the typical ALD process
Summary
The demand for thin-film transistors (TFTs) with high performance has been increasing due to the need for low power consumption, ultra-high pixel density, good form factor, and interactive functionality. Magnetron sputtering is currently mainly used for depositing the a-IGZO channel layer because it allows a low-temperature process and good productivity of a facile a-IGZO film with a cation composition close to that of the sputtering target material. The cation-composition-dependent performances of the a-IGZO TFTs were explained by analyzing the distribution of the density of states (DOS) in a band gap, which were extracted by measuring the temperature-dependent independent variable (IV) characteristics based on the Meyer-Neldel rule (MN rule). Such experimental DOS profiles for the various IGZO TFTs were confirmed via Technology Computer-aided Design (TCAD) simulation
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