Synergistically Enhanced Performance and Reliability of Abrupt Metal‐Oxide Heterojunction Transistor

The large-area low-temperature processing capability and versatile characteristics of amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) are highly expected to promote the developments of next-generation displays, 3D integrated circuit (3DIC), flexible chips, and electronics. However, the abundant native defects in AOSs engrain an inherent trade-off between high mobility and trustworthy stability in AOS TFTs, fundamentally limiting the performance metrics and integration scale of oxide-based electronics. To surmount this obstacle, the bilayer AOS channel is highly expected to combine the merits of diversified AOSs, while the efficiency of such an AOS "heterojunction" is debatable. This work systematically compares the TFTs based on amorphous InGaZnO (a-IGZO), amorphous InZnO (a-IZO), and a-IZO/a-IGZO bilayer. The active cation interaction between metal-oxide semiconductors gives rise to a mixed AOS layer rather than a heterojunction channel, corresponding to moderate performance metrics. Such a spontaneous cation interdiffusion is effectively prevented using a dense metal-oxide dielectric interlayer, aluminum oxide (AlOx). The sharpened interface effectively forms an abrupt metal-oxide heterojunction, while the electron can still tunnel through the ultrathin AlOx to create a quantum well of 2D electron gas (2DEG). The overall performance and reliability of multilayer AOS TFT are synergistically enhanced using the proposed abrupt metal-oxide heterojunction architecture.