A Normally-on Micro-LED Array Driven by Integrated Carbon Nanotube Transistors

Abstract

As micro-light-emitting diode (Micro-LED) pixel dimensions continue to scale down, compact driving devices that can be directly integrated with GaN light-emitting diodes are increasingly required. Here, we employ a monolithic integration scheme in which the underlying n-GaN layer serves as both the Micro-LED cathode and a buried bias electrode for the p-type carbon nanotube thin-film transistor (CNT TFT), thereby constructing a normally-on CNT TFT/Micro-LED pixel architecture. The negatively biased n-GaN layer electrostatically turns on the CNT channel through the intervening dielectric. Compared with conventional local-gate control, n-GaN control maintains comparable switching behavior, with a 10.1% increase in average subthreshold swing and an average threshold-voltage shift of 0.18 V across 60 devices. The CNT TFT is further integrated with a Micro-LED to form a one-transistor–one-diode (1T1D) CNT TFT/Micro-LED pixel, exhibiting clear gate-controlled current modulation and reproducible switching behavior. Based on this architecture, a 3 × 3 CNT TFT/Micro-LED array was fabricated as a proof-of-concept demonstration. Under data-line selection and with no scan signal applied, the corresponding columns operate in a normally-on state, while applied scan voltages modulate or suppress emission at selected data-line/scan-line intersections. This work demonstrates a normally-on, scan-suppressed addressing mode and provides a compact strategy for monolithic GaN/CNT optoelectronic integration without device transfer or bonding.