Optical characterization of point defects on internal quantum efficiency in AlGaN quantum wells grown on face-to-face-annealed sputtered AlN templates

Abstract

The correlation between the internal quantum efficiency (IQE) and the effective diffusion length estimated by the cathodoluminescence intensity line profile near the dark spots, including the effect of non-radiative recombination due to point defects, was experimentally clarified for AlGaN multiple quantum wells (MQWs) on face-to-face annealed (FFA) sputter-deposited AlN templates with different IQEs and similar dislocation densities. The IQEs, which were determined by temperature- and excitation-power-dependent photoluminescence measurements, were independent of the dark spot densities and increased with increasing effective diffusion length (Leff) estimated from the cathodoluminescence line profile analysis. These results suggested that the IQEs of the MQW/FFA samples were governed by the point defect density. The fitting results for the relationship between IQE and Leff and for that between IQE and Cmax explained the experimental results qualitatively.

Localized Surface Plasmonic Resonance of an Al Nanorod Array on High-Quality AlN Templates into the Far-UVC Spectral Region

“…However, the external quantum efficiency (EQE) of far-UVC LEDs is still very low (EQE < 2%). − There are many roots in the low EQE of far-UVC LEDs. For example, the light extraction efficiency (LEE) is low due to the absorptive p-contact and dominant transverse-magnetic mode radiation; the carrier injection is poor due to the low carrier concentration of Al-rich AlGaN alloy; − the internal quantum efficiency (IQE) is compromised due to the high threading dislocation density and point defects in the active region. , Various strategies have been proposed to mitigate the inherently low IQE of AlGaN-based deep-UV LEDs, including adopting high-quality templates, strain management, morphology control, and device dimension reduction. − Coupling the radiative dipole in the active region to vicinal metal nanoparticles is also proposed to improve the LEE and IQE simultaneously. If the dipole oscillation is coupled to the local surface plasmonic resonance (LSPR) at the edge of vicinal metal nanoparticles, the radiative recombination lifetime will be effectively suppressed so that the overall IQE can be improved.…”