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 mu A to 1.1 mA, field effect mobility of from 1.9 to 59.2 cm(2)/Vs, subthreshold swing (SS) of from 278 to 118 mV/dec, and on/off current ratio of from 8.55x10(7) to 4.41x10(9). 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.