Engineers invent vertically stacked, full-color microscopic LEDs

Good news! This could be a significant breakthrough in display technology! When virtual reality becomes reality! 😊

"... But much like computer transistors, LEDs are reaching a limit to how small they can be while also performing effectively. This limit is especially noticeable in close-range displays such as augmented and virtual reality devices ...
Each stacked pixel can generate the full commercial range of colors and measures about 4 microns wide. The microscopic pixels, or “micro-LEDs,” can be packed to a density of 5,000 pixels per inch. ...
“With our vertical micro-LEDs, you could have a completely immersive experience and wouldn’t be able to distinguish virtual from reality.” ...
But micro-LED fabrication requires extreme accuracy, as microscopic pixels of red, green, and blue need to first be grown separately on wafers, then precisely placed on a plate, in exact alignment with each other in order to properly reflect and produce various colors and shades. Achieving such microscopic precision is a difficult task, and entire devices need to be scrapped if pixels are found to be out of place. ..."

From the abstract:

"Micro-LEDs (µLEDs) have been explored for augmented and virtual reality display applications that require extremely high pixels per inch and luminance. However, conventional manufacturing processes based on the lateral assembly of red, green and blue (RGB) µLEDs have limitations in enhancing pixel density. Recent demonstrations of vertical µLED displays have attempted to address this issue by stacking freestanding RGB LED membranes and fabricating top-down, but minimization of the lateral dimensions of stacked µLEDs has been difficult. Here we report full-colour, vertically stacked µLEDs that achieve, to our knowledge, the highest array density (5,100 pixels per inch) and the smallest size (4 µm) reported to date. This is enabled by a two-dimensional materials-based layer transfer technique that allows the growth of RGB LEDs of near-submicron thickness on two-dimensional material-coated substrates via remote or van der Waals epitaxy, mechanical release and stacking of LEDs, followed by top-down fabrication. The smallest-ever stack height of around 9 µm is the key enabler for record high µLED array density. We also demonstrate vertical integration of blue µLEDs with silicon membrane transistors for active matrix operation. These results establish routes to creating full-colour µLED displays for augmented and virtual reality, while also offering a generalizable platform for broader classes of three-dimensional integrated devices."

Engineers invent vertical, full-color microscopic LEDs | MIT News | Massachusetts Institute of Technology Stacking light-emitting diodes instead of placing them side by side could enable fully immersive virtual reality displays and higher-resolution digital screens.

Vertical full-colour micro-LEDs via 2D materials-based layer transfer (no public access)