Ultra-low-defect homoepitaxial micro-LEDs with enhanced efficiency and monochromaticity for high-PPI AR/MR displays

Yibo Liu; Guobin Wang; Feng Feng; Mengyuan Zhanghu; Zhengnan Yuan; Zichun Li; Ke Xu; Hoi Sing Kwok; Zhaojun Liu

doi:10.1186/s43074-024-00137-4

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Yibo Liu, Guobin Wang, Feng Feng, Mengyuan Zhanghu, Zhengnan Yuan, Zichun Li, Ke Xu, Hoi Sing Kwok, Zhaojun Liu. Ultra-low-defect homoepitaxial micro-LEDs with enhanced efficiency and monochromaticity for high-PPI AR/MR displays[J]. PhotoniX. doi: 10.1186/s43074-024-00137-4

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Ultra-low-defect homoepitaxial micro-LEDs with enhanced efficiency and monochromaticity for high-PPI AR/MR displays

doi: 10.1186/s43074-024-00137-4

1.
Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong SAR, China
2.
Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, China
3.
Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Jiangsu Institute of Advanced Semiconductors, Suzhou, China

Funds: The authors would like to thank Shenzhen Sitan Technology, Nanosystem Fabrication Facility (NFF) and E-pack Lab in HKUST for technical support to accomplish the fabrication and characterization in this work. The authors would also like to thank Dr. Zhibo Sun, and Prof. Jr-Hau He from CityU of Hong Kong for their valuable discussion.

Received Date: 2024-04-12
Accepted Date: 2024-07-15
Rev Recd Date: 2024-07-02

Available Online: 2024-08-14

Abstract

Abstract

The issue of brightness in strong ambient light conditions is one of the critical obstacles restricting the application of augmented reality (AR) and mixed reality (MR). Gallium nitride (GaN)-based micro-LEDs, renowned for their exceptional brightness and stability, are considered the foremost contenders for AR applications. Nevertheless, conventional heteroepitaxial growth micro-LED devices confront formidable challenges, including substantial wavelength shifts and efficiency droop. In this paper, we firstly demonstrated the high-quality homoepitaxial GaN-on-GaN micro-LEDs micro-display, and thoroughly analyzed the possible benefits for free-standing GaN substrate from the material-level characterization to device optoelectronic properties and micro-display application compared with sapphire substrate. The GaN-on-GaN structure exhibits a superior crystal quality with ultra-low threading dislocation densities (TDDs) of ~ 10⁵ cm⁻², which is three orders of magnitude lower than that of GaN-on-Sapphire. Through an in-depth size-dependent optoelectronic analysis of blue/green emission GaN-on-GaN/ Sapphire micro-LEDs from 100 × 100 shrink to 3 × 3 μm², real that a lower forward voltage and series resistance, a consistent emission wavelength (1.21 nm for blue and 4.79 nm for green @ 500 A/cm²), coupled with a notable reduction in efficiency droop ratios (15.6% for blue and 28.5% for green @ 500 A/cm²) and expanded color gamut (103.57% over Rec. 2020) within GaN-on-GaN 10 μm micro-LEDs. Last but not least, the GaN-on-GaN micro-display with 3000 pixels per inch (PPI) showcased enhanced display uniformity and higher luminance in comparison to its GaN-on-Sapphire counterpart, demonstrating significant potentials for high-brightness AR/MR applications under strong ambient light.

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