Enhanced performance of large‐area vertical light‐emitting diodes treated by laser irradiation

Abstract

In this work, a comparative analysis of vertical light-emitting diodes (VLEDs) examining the device properties is performed with different surface treatment schemes. The VLEDs on graphite substrate are fabricated by the laser lift-off and the wafer bonding processes. The significance of KrF laser irradiation to form protrusions on the surfaces of undoped gallium nitride (u-GaN) and n-GaN is analysed in detail. The light output power of the fabricated VLEDs is significantly increased through the formation of micro-sized protrusions by the laser irradiation. For VLED irradiated with an energy density of 600 mJ/cm 2 on n-GaN surface with a thin u-GaN layer, the light output power is improved by 24.8% at 350 mA without degradation of electrical properties compared with that of the conventional VLED.

Size-Dependent Quantum Efficiency of Flip-Chip Light-Emitting Diodes at High Current Injection Conditions

“…This technical route has certain drawbacks, in which the yield and the costs during the production are the leading ones, as the sapphire substrates need to be removed by a laser lift-off process that would induce damages to the thin-films transferred. Another technical route is to use ultra-large mesa thin-film LEDs (usually in several mm 2 scale), which aims to push the working current density to the lower end, where the droop effect could be significantly alleviated, in order to achieve higher quantum efficiency even at high current injection conditions [33,34]. However, with this method, the mesa size must be so greatly enlarged that it will induce severe current crowding effect, particularly on the p-side, leading to a degradation in both internal quantum efficiency and light extraction efficiency [35,36].…”