Enhancement of InGaZnO Thin-Film Transistors by Contact Barrier Modulation Using Oxygen Defects

We have studied the effect of barrier-controlled electrodesoncharacteristics of amorphous InGaZnO (a-IGZO) thin-film transistors(TFTs) using an interlayer with modulated oxygen defects. Interlayersof a-IGZO with different electrical resistivities were controlledwith various oxygen ratios during the RF sputtering deposition. Asthe ratio of O-2/(O-2 + Ar) was increased from0 to 20%, the carrier concentration decreased from 2.84 x 10(18) to 1.56 x 10(14) cm(-3) andthe electrical resistivity increased from 0.12 to 9600 & omega;& BULL;cm.Using this result, a-IGZO thin layers with different resistivities(low and high) to control the contact barriers were inserted betweenthe a-IGZO TFT channel and both the source and drain electrodes. Inthe case of a-IGZO TFT with a low resistivity interlayer, the thresholdvoltage (V (th)) was shifted by -4.1V compared to the reference device without an interlayer. In addition,on/off ratio, the subthreshold swing, and the mobility of the deviceswere also enhanced by achieving Ohmic contact. In contrast, the a-IGZOTFT with a high resistivity interlayer showed a positive V (th) shift of 1.5 V and also improved device performance,while maintaining a mobility of & SIM;84% of the reference devicedue to the energy barrier.