LED Electrode Pad Insulation Layer Current Spreading
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Solution Overview
Problem
GaN-based light emitting diodes (LEDs) face issues with current crowding near electrode pads due to high resistivity in the P-type semiconductor layer, leading to uneven current distribution and reduced luminous efficacy, especially in larger LEDs, where defects like threading dislocations can further disrupt uniform current spreading.
Innovation Solution
The design incorporates an insulation layer between the P-type semiconductor layer and the P-electrode pad, along with upper and lower extensions electrically connected to the electrode pads, which helps in dispersing current more uniformly across the LED surface, reducing current crowding and enhancing light emission area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent electrode layer is formed on the P-type semiconductor layer to enhance current spreading, then current spreading is improved, but light absorption increases and thickness is limited
Solution Approach 1:
An insulation layer is introduced as an intermediary between the P-type semiconductor layer and the P-electrode pad. This insulation layer has lower resistivity than the P-type semiconductor layer, enabling it to serve as a mediator for current distribution. The insulation layer disperses current from the electrode pad before it enters the P-type semiconductor layer, improving current spreading without requiring a thick transparent electrode layer that would absorb light.
2Area of moving object
If the size of LED is increased to meet demand, then light output increases, but current crowding and defects become more severe
Solution Approach 1:
The electrode pad structure is segmented into multiple components: the P-electrode pad, the insulation layer, and extensions. The extensions branch out from the main electrode pad and are connected to the P-type semiconductor layer at multiple points. This segmentation allows current to be distributed through multiple pathways across the LED structure, preventing current crowding in any single region and maintaining uniform current distribution even in large-area LEDs.
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 configuration improves current spreading and light extraction efficiency by reducing current crowding and defects, maintaining uniformity and efficacy even in larger LEDs, while minimizing light absorption by the electrode layers.
Implementation Method 1
electric current supplied from the P-electrode pad may be dispersed by the transparent electrode layer before entering the P-type semiconductor layer
Implementation Method 2
extensions extending from the electrode pads may be used to enhance current spreading
Data Source
AI summary
The present invention relates to a light emitting diode including a substrate, a first conductive type semiconductor layer arranged on the substrate, a second conductive type semiconductor layer arranged on the first conductive type semiconductor layer, an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer, a first electrode pad electrically connected to the first conductive type semiconductor layer, a second electrode pad arranged on the first conductive type semiconductor layer, and an insulation layer disposed between the first conductive type semiconductor layer and the second electrode pad, the insulation layer insulating the second electrode pad from the first conductive type semiconductor layer. At least one upper extension may be electrically connected to the second electrode pad, the at least one upper extension being electrically connected to the second conductive type semiconductor layer.