Sundiode Inc of Campbell, CA, USA, a Silicon Valley-based company developing micro-LED technologies for display applications including augmented reality (AR) and mixed reality (MR), has demonstrated a full-color micro-display, consisting of a stacked 3-color (RGB) micro-LED pixel array driven with an active-matrix silicon CMOS backplane.

Following the announcement in late April of a stacked-RGB micro-LED pixel technology patented by Sundiode and developed in collaboration with KOPTI (Korea Photonics Technology Institute), a micro-display using the stacked-RGB pixels was recently achieved using a full-color-capable Si CMOS backplane from Jasper Display Corp of Santa Clara, CA, USA. The compact 15.4mm x 8.6mm display has an array of stacked-RGB micro-LED pixels on a single chip bonded directly onto a Si CMOS backplane in its entirety, completely avoiding conventional pick-and-place processes required for transferring discrete R, G and B subpixels.

The development demonstrates full-color operation of a micro-display with significantly enhanced utilization of the small pixel area of a micro-display. In this display, the pixels are 100μm in size, resulting in a resolution of about 200PPI. The next phase of the development is currently underway to significantly increase the pixel density, in full color, to be suitable for the AR and MR applications.

Pictures: A micro-display with a stacked-RGB pixel array, where each pixel is an RGB-emitting stacked microLED device (left). The micro-display showing a video of fireworks at night, demonstrating the full-color capability (right). N.B. Areas around the display appear dark due to the capturing camera’s exposure being turned down to avoid image saturation.

The fully functional display shows the operation of a stacked-RGB pixel array together with a Si CMOS backplane and, as such, is reckoned to be a crucial milestone in the development towards ultra-high-resolution full-color micro-displays. With the development of epitaxial and fabrication technologies enabling the stacked-RGB pixel device, this demonstration is a step on the way to manufacturing micro-displays based on micro-LEDs that are suitable for AR, MR, and Metaverse.

Jasper Display Corp is a fabless IC design company providing CMOS backplane technology supporting micro-LED development. Jasper Display offers FHD and 4K-resolution backplanes, with what is claimed to be excellent current uniformity and flexible addressing. By working with Sundiode to showcase its 100μm stacked-RGB micro-LED in a single-panel full-color display, Jasper Display demonstrated that its CMOS backplane technology for micro-LEDs can be customized to support needs ranging from low-power AR all the way up to automotive headlights, all with custom resolutions.

Sundiode plans continued development efforts towards the ultra-high-resolution micro-displays using the stacked-RGB pixel technology.