Photonics Technology Center

A world-first 1700 pixels per inch (PPI) passive-matrix (PM) blue micro-display

The first 1700 pixels per inch (PPI) blue passive-matrix light-emitting diodes on silicon micro-displays powered by ASIC with 6-bit grayscale is realized by flip-chip bonding of a micro-LED array onto a CMOS-based ASIC display driver. The micro-display consists of 256 x 192 pixels within a display area of 0.19 inch in diagonal.

Fig.1. (a) I-V curve of single pixel with inset of its light emitting image. (b) Architecture of ASIC driver. Top-down view of (c) ASIC driver and (d) 256 × 192 LEDs array. (e) Final assembly wire-bonded on a flex cable. (f) Source images (top) and its corresponding display images (bottom) on this micro-display.

Related publications:

1. W. C. Chong, W. K. Cho, Z. J. Liu, C. H. Wang, and K. M. Lau, "1700 pixels per inch (PPI) passive-matrix micro-LED display powered by ASIC," in Technical Digest - IEEE Compound Semiconductor Integrated Circuit Symposium, CSIC, 2014.

2. K. M. Lau, Z. Liu, W. C. Chong, W. K. Cho, and C. H. Wang, "Passive-matrix light-emitting diodes on silicon micro-display," ed: Google Patents, 2019.

400 × 240 active-matrix (AM) blue micro-display

A blue GaN micro-LED array featuring 400 × 240 pixels with a pixel size of 30 × 30 μm2 was implemented on a single sapphire substrate using monolithic fabrication process. Active-matrix driving was achieved by hybridizing the micro-LED array with a CMOS backplane.

Fig.2. (a) Layout of 400 × 240 LEDs array and (b) zoomed-in image of LED array edge area. (c) I-V curve of single pixel. (d) Final assembly wire-bonded on PCB driving board. (e) 16-level gray scale images shown on this micro-display.

Related publications:

1. X. Li, L. Wu, Z. Liu, B. Hussain, W. C. Chong, K. M. Lau, et al., "Design and Characterization of Active Matrix LED Microdisplays With Embedded Visible Light Communication Transmitter," Journal of Lightwave Technology, vol. 34, pp. 3449-3457, 2016/07/15 2016.