Effects of atomik layer deposition passivation on leakage current in (In) GaN multi-quantum well light emitting diodes

One of the frequent problems seen in the production of Gallium Nitride (GaN) / Indium Gallium Nitride (InGaN)-based light emitting diodes (LEDs) is leakage current. Leakage current lowers the external quantum efficiency. It may occur due to the defects during epitaxial growth, or due to surface defects that ocur after the mesa structure has been etched during micro-fabrication. In this study, three, four- and six-sidewall LEDs were produced to show the effect of mesa etch on leakage current. Among them, LEDs in six-shaped structure had the highest leakage current. Dangling bonds that appear after dry or wet etching of mesa walls can be passivated with various thin film coatings. The passivation effect of aluminum oxide (AI2O3) films coated with atomic layer deposition (ALD) on the surface states of the side walls was investigated. LEDs with side wall passivation with plasma-assisted chemical vapor deposition (PECVD) were compared with LEDs passivated with ALD growth films. It has been observed that passivation with ALD caused less leakage current than that passivated with PECVD. Moreover, the light output power and light intensity are better in LEDs passivated with ALD. Surface defects on the side walls are passivated better with ALD, increasing the lifetime of the LEDs improving both optical and electrical characteristics. Finally, the study discusses the mechanisms that enables decrease of leakage current.