Active-Matrix GaN µ-LED Display Using Oxide Thin-Film Transistor Backplane and Flip Chip LED Bonding

A 2 in. active-matrix light-emitting diode (AMLED) display by integration of the micro-LED onto the oxide thin-film transistor (TFT) backplane using flip chip bonding is reported. A blue-emitting micro-LED (µ-LED) with a size of 90 × 50 µm ² is fabricated on the GaN epi grown on a sapphire substrate. The amorphous indium-gallium-zinc-oxide (a-IGZO) TFT on glass exhibiting the mobility of 18.4 cm ² V ⁻¹ s ⁻¹ , turn-on voltage (V _ON ) of 0.2 V, and subthreshold swing 0.25 V dec ⁻¹ , is used for LED backplane. A two TFT and one capacitance pixel structure is utilized for driving 128 × 384 AMLED with 120 Hz frame rate. The laser lift-off process with flip-chip bond allows the transfer of the µ-LED chips with 49 152 pixels onto the TFT backplane, demonstrating a 2 in. AMLED display with a good gray scale image. The current efficiency of µ-LED is found to be 12.9 Cd A ⁻¹ at the luminance of 630 Cd m ⁻² . Therefore, a-IGZO TFT backplane can be used for µ-LED displays.