Electrical and Optical Characteristics of 395 nm InGaN-Based Ultraviolet-A Micro-Light Emitting Diodes with Different Sidewall Passivation Methods

This study examines the impact of different sidewall passivation methods on the electrical and optical characteristics of 395 nm ultraviolet-A (UV-A) microlight-emitting diodes (μLEDs). Silicon dioxide deposited by plasma-enhanced chemical vapor deposition, aluminum oxide deposited by plasma-enhanced atomic layer deposition, and aluminum oxide deposited by thermal atomic layer deposition (thermal ALD) were compared as representative sidewall passivation methods. All devices were fabricated on the same epitaxial wafer through an identical top-down process flow, with mesa sizes ranging from 30 to 100 μm. Differences were observed in current–voltage behavior, ideality factor, surface and bulk current components, light output power, and external quantum efficiency. Among the three passivation conditions, the thermal ALD Al 2 O 3 devices showed lower leakage current, lower ideality factor, a smaller surface-current contribution, and smaller optical degradation as the device size decreased. These results provide a comparative data set for discussing sidewall-related behavior in UV-A μLEDs.