AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes With Varied Thickness of Sidewall Passivation via Atomic Layer Deposition

In this study, we fabricated deep-ultraviolet light-emitting diodes (DUV-LEDs) with Al2O3 films of 0-, 130-, and 255-nm via atomic layer deposition (ALD). In addition, the effects of the passivation layers on the DUV-LEDs were systematically investigated. The current–voltage characteristics of these samples revealed the passivating effect of the Al2O3 ALD films on the DUV-LEDs. By analyzing the external quantum efficiency (EQE) at room temperature using the ABC +
${f}\,{(n)}$
model, the differences in the physical mechanisms of the Al2O3 ALD film on DUV-LEDs were determined. The measurements of the electroluminescence (EL) and far-field radiation patterns (EQE, light output power (LOP), and radiation patterns) showed that ALD can enhance the performance of DUV-LEDs, particularly DUV-LEDs with a 130-nm Al2O3 ALD passivation layer. Moreover, the aging test and failure ratio of these DUV-LEDs under humidity exposure (85 °C/85% RH) indicated the specific effect of these Al2O3 ALD films on the reliability of DUV-LEDs.