High-Performance Coplanar Dual-Channel a-InGaZnO/a-InZnO Semiconductor Thin-Film Transistors with High Field-Effect Mobility

An amorphous indium gallium zinc oxide (a-IGZO) layer is deposited on very thin conductive amorphous indium zinc oxide (a-IZO) thin film to demonstrate high-performance, coplanar thin-film transistors (TFTs) with dual-channel oxide semiconductor architecture. Based on material properties, a conduction band offset ( increment E-C) of approximate to 0.28 eV between a-IZO and a-IGZO layers and a conduction band bending of approximate to 0.3 eV at a-IGZO/gate insulator (GI) interface exist. Through the electrical characterization, high field-effect mobility (mu(FE)) of approximate to 50 cm(2) V-1 s(-1), a positive threshold voltage (V-Th) of approximate to 2.3 V, and low off-current (I-OFF) of <1 pA in coplanar a-IZO/a-IGZO TFT are demonstrated. The electron accumulation (>5 x 10(18) cm(-3)) at both the a-IZO/a-IGZO and a-IGZO/GI interfaces confirm the dual-channel conduction. The bottom a-IZO channel significantly contributes to increasing drain current (I-D) due to large electron density (approximate to 10(19) cm(-3)). The dual-channel coplanar TFT with a-IGZO/IZO provides a guideline for overcoming the trade-off between high mu(FE) and positive V-Th control for stable enhancement mode operation with increased I-D.