A Buried High<i>k</i>Insulator for Suppressing the Surface Recombination for GaN-Based Micro-Light-Emitting Diodes
Muyao Zhang, Sheng Hang, Chunshuang Chu, Hua Shao, Yidan Zhang, Yonghui Zhang, Yandi Zhang, Quan Zheng, Qing Li, Zi‐Hui Zhang
Abstract
The external quantum efficiency (EQE) for InGaN/GaN micro-light-emitting diodes ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LEDs) is strongly affected by surface recombination at mesa sidewall. In this work, we propose fabricating a Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> buried insulator in the periphery for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LED mesa to suppress the surface recombination. The Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> buried insulator with a large relative dielectric constant of 26 can significantly reduce the voltage drop in the insulator so that the lateral energy band below the p-type contact can be bent in the way of generating energy barriers for holes in the mesa edge. This further suppresses the current diffusion to the defected mesa edges for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LEDs. Thus, when compared with the reference <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LED, the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LED with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40\times 40\,\,\mu \text{m}^{{2}}$ </tex-math></inline-formula> chip area increases the EQE by 34.6%, and the ON/ OFF current ratio is increased to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{8}}$ </tex-math></inline-formula> . A reduced ideality factor of 6.8 is also obtained when compared with other devices.