Active-matrix micro-light-emitting diode displays driven by monolithically integrated dual-gate oxide thin-film transistors

Abstract

We demonstrate a reliable monolithic process to fabricate micro-light-emitting diodes (μLEDs) driven by highly stable dual-gate structured amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) arrays. In contrast to the conventional μLED integration technologies that require the mass transfer of LEDs, our unique monolithic fabrication of oxide TFTs on the GaN epitaxial layer can be applied for accurate integration compared to the method of mounting discrete μLEDs on a backplane individually. To evaluate the applicability of the method at the wafer level, we introduced an atomic-layer-deposited Al₂O₃ insulator film and a denser oxide semiconductor in a dual-gate structured TFT. The induction of controlled hydrogen diffusion from the gate insulator into the active layer at low temperatures led to the good performance of the dual-gate bottom-contact (DGBC) a-IGZO TFTs under positive bias temperature stress (PBTS), negative bias illumination stress (NBIS), and negative bias temperature illumination stress (NBTIS). Monolithic integration of such μLEDs and DGBC a-IGZO TFT arrays was achieved using an organic interlayer dielectric at a low temperature below 230 °C. This simple process exhibits excellent TFT manufacturability (stable V_on = 0.78 V), stability (ΔV_on, PBTS: 0.03 V, NBIS: −1.85 V, and NBTIS: −3.27 V), uniformity, and reproducibility (less than 4% difference in V_on). It shows promise for the mass production of μLED displays for flexible and/or ultra-high-resolution displays for augmented and virtual reality and biomedical applications.