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Size-controlled InGaN/GaN nanorod LEDs with an ITO/graphene transparent layer
Jae-Phil Shim1, Won-Seok Seong, Jung-Hong Min
1School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Korea. Center for Spintronics, Korea Institute of Science and Technology (KIST), 5 Hwarang-ro 14 gil, Seongbuk-gu, Seoul 02792, Korea.
We developed a new transparent conductive layer using indium tin oxide on graphene for improved indium gallium nitride/gallium nitride (InGaN/GaN) nanorod light-emitting diodes (LEDs). This method enhances light extraction efficiency and current spreading for brighter, more uniform LED performance.
Area of Science:
- Materials Science
- Optoelectronics
- Nanotechnology
Background:
- Indium Gallium Nitride (InGaN)/Gallium Nitride (GaN) nanorod light-emitting diodes (LEDs) are crucial for efficient light generation.
- Achieving high light-extraction efficiency and uniform current spreading in nanorod LEDs remains a challenge.
- Existing methods often involve complex fabrication steps or passivation layers.
Purpose of the Study:
- To introduce a novel current-spreading layer using indium tin oxide (ITO) on graphene for InGaN/GaN nanorod LEDs.
- To achieve passivation-free fabrication and enhance light-extraction efficiency.
- To improve current spreading and light emission uniformity in nanorod LED devices.
Main Methods:
- Fabrication of parallel-nanorod LEDs with a transferred graphene layer on InGaN/GaN nanorods.
- Deposition of indium tin oxide (ITO) on the graphene layer to form a transparent conductive contact.
- Potassium hydroxide (KOH) treatment to reduce series resistance, recover plasma-damaged regions, and control nanorod size.
- Electroluminescence (EL) measurements to assess light emission and strain relaxation.
Main Results:
- The ITO/graphene layer acted as a bridge structure, effectively blocking ITO diffusion and enabling transparent contact without filling air gaps.
- Lateral current spreading by the ITO/graphene layer resulted in uniform light emission across the entire top surface.
- KOH treatment reduced series resistance and reverse leakage current by recovering plasma-damaged regions.
- Varying KOH treatment time controlled nanorod size and induced strain relaxation, observed as a blueshift in EL.
- Bridge-structured LEDs with 8 minutes of KOH treatment exhibited a 15-fold increase in light-emitting efficiency compared to those treated for 2 minutes.
Conclusions:
- ITO on graphene provides an effective passivation-free current-spreading layer for InGaN/GaN nanorod LEDs.
- The developed method significantly enhances light-extraction efficiency and uniformity.
- KOH treatment is a viable method for optimizing nanorod LED performance by managing resistance, damage, and strain.
