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 (mu-LED) with a size of 90 x 50 mu m(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 x 384 AMLED with 120 Hz frame rate. The laser lift-off process with flip-chip bond allows the transfer of the mu-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 mu-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 mu-LED displays.