Current Research

Monolithic micro-LED full-color micro-display

40 × 40 passive-matrix (PM) full-color micro-display using dual-wavelength LED epilayers

The novel dual wavelength LED epilayers were grown on c-plane sapphire substrate in our MOCVD system. A passive-matrix full-color micro-display was monolithically fabricated on the blue/green dual wavelength LED epi-layers, using red quantum dot (QD) photoresist as a color conversion layer which was patterned by photolithography process. The full-color micro-display consisted of 40 × 40 pixels and each pixel included RGB subpixels with pitch size of 40 μm × 120 μm.

Fig.1. (a) Structure of dual wavelength LED epi-wafers. (b) A 320 μm-diameter circular LED testing device. (c) EL spectra at different injection currents of the testing device.

Fig.2 (a) EL spectra of RGB subpixels with CF. Inset: Photos of RGB subpixels. (b) CIE 1931 chromaticity diagram of RGB subpixels. (c) Displayed images.

Related publications:

  1. P. Li, X. Zhang, Y. Li, L. Qi, C. W. Tang, K. M. Lau, "Monolithic Full-color Micro-display Using Patterned Quantum Dot on Dual Wavelength LED Epi-layers," under review.

32 x 18 active-matrix (AM) full-color micro-display using GaN-on-Si blue LED epilayers

An active matrix monolithic micro-LED full-color micro-display with a pixel density of 317 ppi is demonstrated. Starting from large-scale and low-cost GaN-on-Si epilayers, monolithic 64 × 36 blue micro-LED arrays are fabricated and further transformed to a 32 x 18 full-color micro-displays by applying a photo-patternable color conversion layer.

Fig.3. Schematic of (a) the blue GaN micro-LED array integrated with the CMOS backplane, and (b) the full-color micro-display with QDs-based color conversion layer

Fig.4. EL spectra when only (a) red, (b) green and (c) blue sub-pixels are powered on, independently. (d) Rendered full-color images.

Related publications:

  1. X. Zhang, L. Qi, W. C. Chong, P. Li, C. W. Tang, K. M. Lau, "Active Matrix Monolithic Micro-LED Full-Color Micro-display," under review.

High-resolution full-color micro-display towards mass production

A high-resolution monolithic micro-LED full-color micro-display was demonstrated, combining the commercial 4-inch GaN-on-Si blue LED epilayers and high-performance QD-PRs.

Fig.5. (a) 4-inch GaN-on-Si wafer after micro-LED process. (b) Image of the micro-LED chip fully powered-on with input current of 100 mA, inset is a zoomed-in image of the display area. (c) Micro-LED chip packaged on the PCB board. (d) Display image with all the pixels powered on and red, green and blue subpixels.

Related publications:

  1. X. Zhang, L. Qi, W. C. Chong, P. Li, K. M. Lau, "High-resolution Monolithic Micro-LED Full-color Micro-display," in SID Symposium Digest of Technical Papers, 2020.