Amorphous In–Ga–Zn–O coplanar homojunction thin-film transistor

A fabrication process of coplanar homojunction thin-film transistors (TFTs) is proposed for amorphous In–Ga–Zn–O (a-IGZO), which employs highly doped contact regions naturally formed by deposition of upper protection layers made of hydrogenated silicon nitride (SiNX:H). The direct deposition of SiNX:H reduced the resistivity of the semiconductive a-IGZO layer down to 6.2×10−3 Ω cm and formed a nearly ideal Ohmic contact with a low parasitic source-to-drain resistance of 34 Ω cm. Simple evaluation of field-effect mobilities (μsat) overestimated their values especially for short-channel TFTs, while the channel resistance method proved that μsat was almost constant at 9.5 cm2 V−1 s−1.