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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 µm2 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 cm2 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.

Highly robust poly-Si thin-film transistor (TFT) on polyimide (PI) substrate using blue laser annealing (BLA) of amorphous silicon (a-Si) for lateral crystallization is demonstrated. Its foldability is compared with the conventional excimer laser annealing (ELA) poly-Si TFT on PI used for foldable displays exhibiting field-effect mobility of 85 cm 2 (V s) À1 . The BLA poly-Si TFT on PI exhibits the field-effect mobility, threshold voltage (V TH ), and subthreshold swing of 153 cm 2 (V s) À1 , À2.7 V, and 0.2 V dec À1 , respectively. Most important finding is the excellent foldability of BLA TFT compared with the ELA poly-Si TFTs on PI substrates. The V TH shift of BLA poly-Si TFT is %0.1 V, which is much smaller than that (%2 V) of ELA TFT on PI upon 30 000 cycle folding. The defects are generated at the grain boundary region of ELA poly-Si during folding. However, BLA poly-Si has no protrusion in the poly-Si channel and thus no defect generation during folding. This leads to excellent foldability of BLA poly-Si on PI substrate.

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The low-temperature polysilicon oxide (LTPO) complementary metal-oxidesemiconductor (CMOS) thin-film transistors (TFTs) is fabricated by p-type lowtemperature polysilicon (LTPS) TFT and n-type amorphous indium-gallium-zinc oxide (a-IGZO) TFT using coplanar structure. A double-stack SiO 2 layer deposited by high temperature first and then low-temperature process is used as a gate insulator for LTPS TFT, leading to reduce the number of photomask steps. The p-channel LTPS TFT of the fabricated LTPO circuits exhibits the field-effect mobility (μ FE) and threshold voltage (V TH) of 89.9 cm 2 (V s) À1 and À5.5 V, respectively. However, the a-IGZO TFT exhibits the μ FE of 22.5 cm 2 (V s) À1 and V TH of À1.3 V. Both the LTPS TFT and a-IGZO TFT show excellent bias stability (ΔV TH of <0.1 V) and zero hysteresis voltage, which reveals the excellent interface between gate insulator and semiconductor. The LTPO CMOS inverter exhibits a gain of 264.5 V V À1 and a high noise margin of 4.29 V, and a low noise margin of 3.69 V at V DD of 8 V. Therefore, the LTPO TFT technology developed in this work can be a promising candidate for low cost, large-area manufacturing of display, and TFT electronics.

We report the active matrix micro-LEDs (AMLEDs) with high brightness over 40,000 cd/m 2 . Active-matrix low temperature poly-Si TFT with mobility over 150 cm 2 /Vs by using blue laser annealing is used for AMLEDs. A 256 pixels micro-LED with ~ 40,000 cd/m 2 at the driving current of 10 mA is fabricated and then 1,024 pixels micro-LED is demonstrated using Au bonding on the LTPS TFT backplane.

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We studied the effect of a‐IGZO thickness (tIGZO) on device uniformity and drain current (ID) of a‐IGZO thin‐film‐transistors (TFTs) driven by the single gate (SG) and dual‐gate driving (DG‐driving). Numerical simulation using fitting density‐of‐states (DOS) exhibits ~5 times larger ID and excellent uniformity with DG‐driving TFTs for a‐IGZO tIGZO<20 nm than SG‐TFT and enables the opportunity of high yield backplanes using DG‐TFTs for next generation high‐performance display applications.