Effects of Rare-Earth Element Dopants in High-Mobility InOx-Based Thin-Film Transistors

The differences between lanthanum and neodymium dopants were investigated with InLaO thinfilm transistor (TFT) and InNdO TFT. Even though InNdO TFT (46.4 cm
²
/Vs) shows higher mobility than that of InLaO TFT (34.7 cm
²
/Vs), the InNdO TFT exhibited inferior stability under negative gate bias stress compared with that of the InLaO TFT, which is ascribed to the |Nd3d
_5/2
5
4f
⁴
O2p
^-1
' charge transfer electron configuration. The |Nd3d
_5/2
5
4f
⁴
O2p
^-1
' charge transfer electron configuration is dominant in the InNdO film and generate holes in the channel layer, leading to serious negative shift of the threshold voltage under negative gate bias stress. On the contrary, the |La3d
_5/2
54f
⁰
' non-charge transfer electron configuration is dominant in the InLaO film, and the InLaO TFT shows better stability under negative gate bias stress.