Active Matrix Monolithic LED Micro-Display Using GaN-on-Si Epilayers

• Published in: IEEE photonics technology letters 2019-06, Vol.31 (11), p.865-868
• Main Authors: Zhang, Xu, Li, Peian, Zou, Xinbo, Jiang, Junmin, Yuen, Shing Hin, Tang, Chak Wah, Lau, Kei May
• Format: Article
• Language: English
• Subjects: Active matrix; Backplanes; Bonding; CMOS; Copper; Crosstalk; Cu/Sn bonding; Display devices; flip-chip; Gallium nitride; Gallium nitrides; GaN-on-Si; Gold; Ion etching; Light emitting diodes; Metal bonding; Metals; micro-display; micro-LEDs array; Pixels; Reactive ion etching; Sapphire; Silicon; Silicon substrates; Substrates; Tin
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2019.2910729

An active matrix light emitting diode (LED) microdisplay system was demonstrated with GaN-on-Si epilayers and a custom-designed CMOS backplane using an Au-free Cu/Snbased metal bonding method. The blue micro-LED array consists of 64 × 36 pixels with a pitch size of 40 μm × 40 μm and a pixel density of 635 pixels/in (ppi). The Si substrate for the LED growth was removed by reactive ion etching (RIE) using SF6based gas after flip-chip bonding. Crack-free and smooth GaN layers in the display area were exposed. Images and videos with 4-bit grayscale could be clearly rendered, and light crosstalk was significantly suppressed compared to its counterpart using the GaN-on-sapphire epilayers. The demonstration suggests the tremendous potential of the low-cost and large-scale GaN-on-Si epilayers and cost-effective Au-free Cu/Sn-based bonding scheme for micro-display applications.