Performance Enhancement of GaN-Based Light-Emitting Diodes by Using Transparent Ag Metal Line Patterns

Abstract

Characteristics of GaN-based light-emitting diodes (LEDs) with 1-D stripe (B-series) and 2-D grid (A-series) Ag metal line patterns are comprehensively studied and reported. Due to the enhanced current spreading capability, as compared to a conventional LED, the significantly reduced forward voltages (>500 mV) of studied A- and B-series devices are obtained under the forward current of 20 mA. Particularly, a very low current coefficient of junction temperature $\text{T}_{\text {j}}$ (~0.03°/mA) could be obtained for studied A- and B-series devices which is remarkably superior to the conventional device (0.61°/mA). It means that the undesired thermal effect is nearly negligible in studied devices. Experimentally, based on the less absorption effect of photons from Ag metal lines, the 1-D stripe design (B-series) shows better optical properties than 2-D grid one (A-series). Therefore, based on the appropriate design of transparent 1-D Ag pattern, the improved performance of GaN-based LEDs, including smaller forward voltage, higher light output power, higher external quantum efficiency, higher wall-plug efficiency, and negligible current dependence (wider current operating regime) could be simultaneously attained.