image: High quality 4-inch green GaN-on -Si epilayers. a, Typical photograph of a 4-inch Si-based epitaxial wafer, where the epitaxial structure is shown on the right side. b, High resolution X-ray diffraction pattern of epilayer grown on Si (111) substrate, where FWHM values of rocking curves corresponding to (002) and (102) are measured to be 277 arcsec and 264 arcsec, showcasing the total dislocation of 5.25×108 cm-2. c, The mapping of wafer bowing condition, which indicates convex bowing of 16.7 μm. d, Wafer mapping of the dominant wavelength on the epilayer, exhibiting high wavelength uniformity (STDEV<1 nm).
Credit: by Haifeng Wu, Xiao Lin, Qin Shuai, Youliang Zhu, Yi Fu, Xiaoqin Liao, Yazhou Wang, Yizhe Wang, Chaowei Cheng, Yong Liu, Lei Sun, Xinyi Luo, Xiaoli Zhu, Liancheng Wang, Ziwei Li, Xiao Wang, Dong Li, and Anlian Pan
In recent years, the field of display technology has witnessed a paradigm shift towards GaN-based Micro-LEDs displays, representing a promising avenue for next-generation visual interfaces. Among the various colors crucial for achieving vibrant and energy-efficient displays, green stands out as particularly significant due to its essential role in accurate color reproduction and overall image quality. However, progress in green Micro-LEDs has been hindered by persistently low energy conversion efficiency, especially with small-size pixels. This limitation poses a significant obstacle in achieving a balanced color spectrum and a considerable overall brightness, crucial for delivering realistic and vibrant visuals in display technologies. In this term, manufacturing green Micro-LEDs with high brightness and high resolution is of great significance.
In a new paper published in Light Science & Applications, a team of scientists, led by Professors Anlian Pan and Dong Li from Hunan University, Changsha, China and co-workers have designed and grown wafer-scale uniform green GaN epilayer on a 4-inch/6-inch Si (111) substrate. This epilayer demonstrated a low dislocation density of 5.25×108 cm-2, minimal wafer bowing of 16.7 μm, and high wavelength uniformity (STDEV<1 nm). Leveraging these advanced materials, they developed green Micro-LEDs with an impressive brightness exceeding 107 cd/m² (nits). Furthermore, the integration of Micro-LEDs with Si-based CMOS circuits enabled the realization of green Micro-LED displays with resolution up to 1080×780, achieving high-definition playback of movies and images. The work lays the foundation for the mass production of high brightness Micro-LED displays on large size GaN-on-Si epi-wafers.
These scientists summarized the highlights of the work as follows:
“(1) A gallium (Ga)-assisted method for AlN growth is proposed in this work to address the challenges of low-temperature preparation of high-quality AlN buffer layers on silicon substrates, resulting in the successful fabrication of high-quality GaN epilayers at the wafer scale. (2) A highly controllable roughening process combined with atomic-level sidewall passivation treatment is implemented, overcoming the bottleneck in Micro-LED luminous efficiency and enabling the production of ultra-high brightness Micro-LEDs. (3) Vertical non-alignment bonding technique is developed, which allows for the seamless integration of Micro-LED displays with Si-based CMOS drivers, achieving exceptional uniformity and high-resolution in micro-displays.”
The scientists further predicted: “With the rapid advancement of GaN-based micro-displays, future technological innovations could accelerate the arrival of the metaverse era.
Article Title
Ultra-high brightness Micro-LEDs with wafer-scale uniform GaN-on-silicon epilayers