Enhanced light extraction from GaN based light-emitting diodes using a hemispherical NiCoO lens

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Gallium nitride (GaN)-based light-emitting diodes (LEDs) are crucial for efficient lighting.
• Improving light extraction efficiency (LEE) is key to enhancing LED performance.
• Nanomaterials offer novel strategies for optical enhancement in LEDs.

Purpose of the Study:

• To investigate the use of Ni(1-x)Co(x)O nanoparticles (NPs) for improving LEE in GaN LEDs.
• To explore a hybrid approach combining Ni(1-x)Co(x)O NPs and ZnO nanorods for further LEE enhancement.
• To analyze the optical and electrical properties of modified GaN LEDs.

Main Methods:

• Fabrication of Ni(1-x)Co(x)O hemispherical lens arrays on p-GaN layers via drop-casting.
• Electroluminescence (EL) and photoluminescence (PL) measurements to assess optical properties.
• Growth of ZnO nanorod arrays on Ni(1-x)Co(x)O NPs for a hybrid structure.
• Finite-difference time-domain (FDTD) simulations to model light propagation.

Main Results:

• Ni(1-x)Co(x)O NPs increased PL and EL intensities by 1.74 and 1.61 times, respectively, compared to conventional LEDs.
• The hybrid structure with ZnO nanorods and Ni(1-x)Co(x)O NPs achieved a 3.8-fold increase in LEE over LEDs with bare Ni(1-x)Co(x)O NPs.
• The hybrid structure demonstrated a 6.2-fold increase in LEE compared to LEDs without any NPs.
• Experimental results were corroborated by FDTD simulations.

Conclusions:

• Ni(1-x)Co(x)O NPs effectively enhance light extraction in GaN LEDs by modifying the escape cone and scattering light.
• The hybrid nanostructure of ZnO nanorods on Ni(1-x)Co(x)O NPs offers a significant advancement in LED light extraction.
• This study presents a promising pathway for developing highly efficient GaN-based optoelectronic devices.