Researchers from Korea University, with colleagues from Shivaji University and Gyeongsang National University, have developed a transparent resistive memory device designed to drive individual microLED pixels, offering an alternative to the thin-film-transistor-and-capacitor circuits used in conventional active-matrix backplanes.
This research targets a persistent problem in transparent microLED displays, where the driving element must combine low off-state current, stable multilevel switching, and high optical transmittance. The researchers say that oxide-based transparent memories tend to exchange oxygen with the indium tin oxide (ITO) electrodes, producing high leakage and unstable switching, while nitride-based devices are more stable at the interface but usually switch abruptly between two states because of deep nitrogen-vacancy traps, making reliable grayscale operation difficult.
The team addressed this by engineering an ultrathin aluminum oxynitride (AlON) transition layer within an aluminum nitride (AlN) switching film. By tuning the reactive sputtering conditions, they controlled oxygen incorporation at the ITO interface to form a stable AlON layer that suppresses leakage pathways and introduces shallow, distributed traps rather than deep ones. The resulting ITO/AlON/AlN device conducts through a Poole-Frenkel mechanism, which lowers off-state current and produces four reproducible resistance states suitable for grayscale modulation. The full stack retains roughly 79 percent optical transmittance in the blue spectral region, and temperature-dependent measurements confirmed that the resistance states stay separated under self-heating. When integrated with a microLED pixel, the device produced stepwise changes in emission intensity without distorting the emission spectrum.
For microLED displays, the approach points toward simpler, more transparent driving schemes. A two-terminal memory element that stores multiple brightness levels could reduce reliance on the multi-transistor pixel circuits and external capacitors that limit aperture ratio and complicate fabrication in transparent panels. High transmittance and the ability to vertically stack the memory on top of the emitter also favour higher integration density, which is relevant to see-through applications such as augmented and virtual reality displays, automotive head-up displays, and smart windows. The demonstration remains at the single-pixel and few-level stage, so scaling the state count, uniformity, and array-level integration will determine how far the concept can move toward practical transparent microLED backplanes.
