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

Amorphous In–Ga–Zn-O (a-IGZO) thin-film transistors (TFTs) with a coplanar homojunction structure are demonstrated. The coplanar source and drain regions made of a-IGZO were formed by depositing a hydrogenated silicon nitride (SiNX:H) layer onto the a-IGZO layer. The a-IGZO regions on which the SiNX:H layer was directly deposited showed the low resistivity of 4.7 × 10−3  Ω cm and degenerated conduction. The fabricated TFT showed excellent transfer and output characteristics with a field-effect mobility of 11 cm2 V− 1 s− 1, a subthreshold swing of 0.17 V decade− 1, and an on-to-off current ratio larger than 1 × 109. The width-normalized source-to-drain resistance (RsdW) calculated using a channel resistance method was 51 Ω cm. This TFT also showed good stability over environment change and under electrical stress.