Performance Enhancement of Amorphous In–Ga–Zn–O Thin Film Transistors with Partial Hetero-Junction Channel Layer

In this work, we fabricated bottom-gate type amorphous In–Ga–Zn–O (a-IGZO) thin film transistors (TFTs) with two local conducting buried extension layers (LCBELs) to improve their electrical characteristics. A LCBEL was formed at both sides of the source/drain (S/D) regions in the a-IGZO channel layer. In particular, the LCBELs enhanced the electrical characteristics of the a-IGZO TFTs by reducing the internal resistance of the channel while decreasing the space between the LCBELs. As a result, compared to the conventional a-IGZO TFTs without the LCBELs, the fabricated a-IGZO TFTs with the embedded LCBELs showed improved electrical characteristics, such as an on current of from 30 μA to 1.1 mA, field effect mobility of from 1.9 to 59.2 cm²/Vs, subthreshold swing (SS) of from 278 to 118 mV/dec, and on/off current ratio of from 8.55 × 10⁷ to 4.41 × 10⁹. Also, in positive and negative bias temperature stress (PBTS and NBTS) tests, the a-IGZO TFTs with embedded LCBELs exhibited good stability compared to the conventional a-IGZO TFTs without the LCBELs.