Analysis of Polarization-Dependent Light Extraction and Effect of Passivation Layer for 230-nm AlGaN Nanowire Light-Emitting Diodes

This paper investigates the polarization-dependent light extraction efficiency (η
_extraction
) and the effect of passivation layer for AlGaN-based nanowire (NW) deep-ultraviolet (DUV) light-emitting diodes (LEDs) emitted at 230 nm using three-dimensional finite-difference time-domain method. Our results show that the use of NW structure for 230-nm LEDs can result in higher transverse-magnetic (TM) polarized η
_extraction
than transverseelectric (TE) polarized η
_extraction
. Specifically, η
_extraction
up to ~48% for TM polarization and ~41% for TE polarization can be achieved by the investigated 230-nm NW LEDs as compared to conventional planar LEDs (~0.2% and ~2% for TM- and TE-polarizations, respectively) attributed to the large surface-to-volume ratio and strong sidewall emissions. In addition, the analysis on the effect of various passivation layer materials suggests the use of SiO
₂
, which has smaller refractive index than the NW core, could extract more photons out of the NW core and lead to TM-polarized η
_extraction
up to ~47%. Therefore, the use of the AlGaN NW structure is expected to lead to high external quantum efficiency DUV LEDs due to the large TM-polarized η
_extraction
in combination with the dominant TM-polarized spontaneous emissions at 230 nm.