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In order to improve EQE, we have investigated on the role of multilayer graphene (MLG) on the electrical and optical properties of GaN based light-emitting diodes (LEDs) with ultrathin ITO (5 nm or 10 nm)/p-GaN contacts. The MLG was transferred on the ITO/p-GaN to decrease sheet resistance of thin ITO p-electrode and improve the current spreading of LEDs. The LEDs with the ITO 5 nm and MLG/ITO 5 nm structures showed 3.25 and 3.06 V at 20 mA, and 11.69 and 13.02 mW/sr at 400 mA, respectively. After forming MLG on ITO 5 nm, the electro-optical properties were enhanced. Furthermore, the GaN based-LEDs applied to the ITO 10 nm, and MLG/ITO (10 nm) structures showed 2.95 and 3.06 V at 20 mA, and 20.28 and 16.74 mW/sr at 400 mA, respectively. The sheet resistance of the MLG transferred to ITO 5 nm was decreased approximately four fold compared to ITO 5 nm. On the other hand, the ITO 10 nm and MLG/ITO 10 nm showed a similar sheet resistance; the transmittance of the LEDs with ITO 10 nm decreased to 16% due to MLG formation on ITO. This suggests that the relationship between the sheet resistance and transmittance according to the ITO film thickness affected the electro-optical properties of the LEDs with a transparent p-electrode with the MLG/ITO dual structure.

We proposed the effects of electron‐beam irradiation (EBI) on the Ag reflector for GaN‐based light‐emitting diodes (LEDs). To evaluate the thermal stability of Ag, we carried out a thermal aging test. The Ag with EBI showed a high reflectance of 97.9% at a 450 nm wavelength and higher thermal stability than the Ag reflector without EBI. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X‐ray diffraction (XRD) were used to examine the surface and texture evolution of the Ag reflector before and after thermal aging at 300 °C for 120 min. SEM and EBSD showed that unlike the agglomeration occurred in the Ag reflector without EBI, the Ag reflector with EBI only showed an increase in grain size after thermal aging at 300 °C for 120 min. XRD data demonstrated the Ag reflector to have a higher <111>‐peak intensity due to EBI. On the other hand, after thermal aging at 300 °C for 120 min, the Ag reflector with EBI becomes less <111>‐peak than the Ag reflector without EBI. The difference in the surface and texture between the Ag reflectors with/without EBI is closely related to the changes in grain size and surface energy by thermal aging.

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