A Buried High k Insulator for Suppressing the Surface Recombination for GaN-Based Micro-Light-Emitting Diodes

The external quantum efficiency (EQE) for InGaN/GaN micro-light-emitting diodes (
$\mu $
LEDs) is strongly affected by surface recombination at mesa sidewall. In this work, we propose fabricating a Ta
₂
O
₅
buried insulator in the periphery for the
$\mu $
LED mesa to suppress the surface recombination. The Ta
₂
O
₅
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
$\mu $
LEDs. Thus, when compared with the reference
$\mu $
LED, the proposed
$\mu $
LED with
$40\times 40\,\,\mu \text{m}^{{2}}$
chip area increases the EQE by 34.6%, and the ON/ OFF current ratio is increased to
$10^{{8}}$
. A reduced ideality factor of 6.8 is also obtained when compared with other devices.