High-mobility vertical thin-film transistors enabling vertically integrated OLED devices for high-density displays

Conventional planar thin-film transistors (TFTs) face fundamental limitations in channel length scaling and output capacity, limiting their application in ultra-high-resolution organic light-emitting diode (OLED) displays. These challenges render planar TFTs unsuitable for next-generation display backplanes, making vertical thin-film transistors (VTFTs) a viable alternative owing to their vertical current paths and enhanced scalability. This study introduces a high-performance VTFT architecture integrated with OLEDs, employing a bilayer active channel consisting of indium‑zinc oxide (IZO) and indium‑gallium‑zinc oxide (IGZO). A 400-nm-thick hafnium oxide (HfO₂) spacer precisely defines the vertical channel length, allowing short-channel operation without relying on advanced lithography. To enhance carrier transport, pulse-induced Joule heating is applied afterward, generating oxygen vacancies and inducing a quasi-two-dimensional electron gas (q-2DEG) at the IZO/IGZO interface. This q-2DEG improves mobility by mitigating electron scattering and strengthening carrier confinement. The resulting VTFT demonstrates excellent electrical characteristics suitable for display applications. By vertically integrating the TFT beneath the OLED and employing a shared drain/anode electrode, the proposed architecture enables compact monolithic integration. This stacked OLED integration reduces the pixel circuit footprint and simplifies the fabrication process, offering a promising route toward densely integrated and high-resolution OLED display technologies.