31.3: Low Optical Crosstalk Micro‐LED Micro‐Display with Semi‐Sphere Micro‐Lens for Light Collimation

Abstract

A 400×240 monochromic micro‐LED micro‐display based on GaN vertical‐LED structure is presented. The micro‐display has the pixel pitch of 30 μm and the size of micro‐LEDs is only 8 μm. It is realized by bonding the GaN epi with the pre‐defined anode pad array to the specific pixel driver on the IC backplane, followed by laser lift‐off and ICP etch process to form isolated micro‐LED pixel array. The electrical connection of n‐type GaN on micro‐LEDs is done by a layer of metal‐grid which serves as a common cathode. Comparing with conventional lateral micro‐LED structure, the vertical‐LED architecture used in our micro‐LED micro‐display is more advantageous of achieving higher device performance such as better current injection, higher light extraction efficiency, low light crosstalk and is more capable of producing compact micro‐LED arrays. In addition, wafer‐level processed semi‐sphere micro‐lens array is also integrated into the micro‐display with each micro‐lens coupled to a single micro‐LED pixel. The micro‐lenses can effectively collimate divergent light emitted from micro‐LEDs leading to a significant improvement of projection brightness when used in a projection light engine. The self‐emissive micro‐LED micro‐display shows its great potentials for projectors and many other applications.