Nitride LED p-electrode spacing for current crowding
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Solution Overview
Problem
Conventional nitride-based semiconductor LEDs face reduced light extraction efficiency and increased local current crowding due to high resistance differences between p-type and n-type semiconductor layers, leading to decreased brightness and reliability.
Innovation Solution
A nitride-based semiconductor LED design with a p-electrode pad spaced 50 to 200 μm from the outer edge of the p-type nitride semiconductor layer, using a transparent electrode like ITO, and a buffer layer of AlN/GaN, to enhance current spreading and reduce local current crowding, thereby expanding the light-emitting area and lowering driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the p-electrode pad is placed close to the outer edge line of the p-type nitride semiconductor layer to maximize light emitting area, then the light emitting area is increased, but local current crowding increases and reliability degrades
Solution Approach 1:
The patent applies local quality by creating a preferential light emission region with distinct properties from other areas. This region is positioned at a specific distance from the p-electrode pad where current density is optimized, allowing high light extraction efficiency without the harmful current crowding effects present near the electrode pad itself.
Solution Approach 2:
The patent resolves the contradiction by transitioning from a two-dimensional placement optimization (maximizing area near the electrode) to a three-dimensional spatial optimization by defining a specific distance range (50-200 μm) from the electrode pad. This dimensional approach allows the light emitting area to be maximized while maintaining reliable current distribution through proper spatial positioning.
2Productivity
If the transparent electrode is used to increase current injection area, then current spreading effect is enhanced, but local current crowding occurs due to high surface resistance
Solution Approach 1:
The patent applies parameter changes by optimizing the distance parameter between the p-electrode pad and the preferential light emission region to be 50-200 μm. This parameter optimization balances the current spreading effect provided by the transparent electrode with the avoidance of current crowding, achieving both enhanced productivity and reduced harmful effects.
Solution Approach 2:
The patent uses the transparent electrode as an intermediary element that enables current injection while the optimized positioning of the light emitting region acts as a mediator that distributes this current effectively. The specific distance positioning allows the transparent electrode to spread current without creating localized crowding effects.
3Productivity
If the p-electrode pad is positioned to maximize light extraction area, then light extraction efficiency is enhanced, but driving voltage increases due to current crowding
Solution Approach 1:
The patent optimizes the positional parameter of the preferential light emission region at 50-200 μm from the p-electrode pad, which simultaneously maximizes light extraction efficiency and minimizes current crowding effects that would otherwise increase driving voltage. This parameter optimization resolves the power-efficiency trade-off.
Solution Approach 2:
By creating a localized preferential emission region with optimized current density characteristics at a specific distance from the electrode pad, the patent achieves high light extraction efficiency in this region without subjecting the entire device to the harmful effects of current crowding, thus maintaining lower driving voltage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances light extraction efficiency, reduces local current crowding, and improves the reliability of the diode by optimizing the placement and distance of the p-electrode pad, resulting in increased optical power and reduced driving voltage.
Implementation Method 1
a transparent electrode 105 is formed on the p-type nitride semiconductor layer 104 so as to increase an injection area of current which is injected through the p-electrode pad 106
Implementation Method 2
group III-V nitride semiconductors such as GaN have excellent physical and chemical properties, they are considered as essential materials of light emitting devices, for example, light emitting diodes (LEDs)
Data Source
AI summary
A nitride-based semiconductor LED includes a substrate; an n-type nitride semiconductor layer formed on the substrate; an active layer and a p-type nitride semiconductor layer that are sequentially formed on a predetermined region of the n-type nitride semiconductor layer; a transparent electrode formed on the p-type nitride semiconductor layer; a p-electrode pad formed on the transparent electrode, the p-electrode pad being spaced from the outer edge line of the p-type nitride semiconductor layer by 50 to 200 μm; and an n-electrode pad formed on the n-type nitride semiconductor layer.