Low-temperature monolithic integration of InGaN µ-LEDs and a-IGZO TFTs

Next-generation near-eye display technologies, including augmented and virtual reality (AR/VR), demand compact, high-resolution, and power-efficient light sources directly integrated with high-performance driver electronics. We present a three-dimensional (3D) monolithic integration of indium gallium nitride (InGaN) micro light-emitting diodes (μ-LEDs) and amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) on a common sapphire substrate. This vertically stacked platform eliminates key limitations of conventional mass-transfer approaches, such as pixel misalignment, limited scalability, and complex assembly. InGaN μ-LEDs with dimensions of 150 × 150 µm2 are fabricated using a top-down etching process, followed by Al2O3 passivation via atomic layer deposition and spin-on-glass planarization to achieve surface uniformity. Subsequently, a-IGZO TFTs are deposited and patterned directly above the μ-LEDs under a low thermal budget (⪅300 °C) to preserve the optical and structural integrity of the emitters. The integrated TFTs exhibit robust switching behavior and adequate current-driving capability, enabling dynamic pixel-level control and demonstrating the potential for energy-efficient AR/VR microdisplays. In addition to μ-LED integration, for the first time nanoscale InGaN LED arrays with 500 nm diameter and an array size of 60 × 60 μm2 were successfully monolithically integrated with a-IGZO TFTs, demonstrating scalability of the platform toward ultrahigh-resolution displays.