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 (mu LEDs) driven by highly stable dual-gate structured amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) arrays. In contrast to the conventional mu LED 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 mu LEDs 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 mu LEDs and DGBC a-IGZO TFT arrays was achieved using an organic interlayer dielectric at a low temperature below 230 degrees C. This simple process exhibits excellent TFT manufacturability (stable V-on = 0.78 V), stability (Delta V-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 mu LED displays for flexible and/or ultra-high-resolution displays for augmented and virtual reality and biomedical applications.