Multi-Tunnel Junction LED with N-Type Contact for Current Spreading
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Solution Overview
Problem
Existing light emitting diodes (LEDs) face challenges in emitting white light due to heat generation, which negatively affects color conversion elements, and they often suffer from limited current spreading and light emitting efficiency, especially when using p-type semiconductor layers.
Innovation Solution
A light emitting diode with multiple tunnel junctions and light emitting structures, where a common n-type semiconductor contact layer enhances current spreading and includes recessed metal contacts on exposed semiconductor layers, allowing for efficient light emission and reduced damage during fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a blue light emitting diode chip is used for white light emission, then white light can be generated, but high heat is generated during operation which negatively affects color conversion phosphors
Solution Approach 1:
The patent divides the light emitting diode into multiple independent light emitting structures (first, second, and third light emitting structures) with different active layers that emit different colors of light. This segmentation allows each structure to operate at optimized conditions, reducing overall heat generation while achieving white light through color combination rather than phosphor conversion from a single high-power blue source
2Illumination intensity
If p-type semiconductor layers are used in light emitting structures, then light emission can be achieved, but current spreading and light emitting efficiency are limited
Solution Approach 1:
The patent changes the doping type parameter of the contact layers from conventional p-type to n-type. This parameter change enables significantly improved current spreading characteristics and light emitting efficiency, as n-type semiconductor layers provide superior electrical conductivity and current distribution compared to p-type layers in LED structures
3Adaptability or versatility
If multiple light emitting structures are stacked to create white light, then phosphor usage can be reduced, but device complexity increases
Solution Approach 1:
The patent merges multiple light emitting structures with different active layers into a single integrated device, where each structure emits a different color (blue, green, red). By combining these structures and their respective tunnel junctions into one device, the patent achieves white light emission through direct color mixing rather than phosphor conversion, while managing complexity through a unified structural design
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
The multi-tunnel junction LED configuration enables the creation of various color combinations, such as blue and green, and suppresses damage to semiconductor layers, improving light emitting efficiency and allowing for white light emission without the need for certain phosphors, while enhancing current spreading and reducing heat-related issues.
Implementation Method 1
a first tunnel junction layer disposed on a lower surface of the common contact layer, a second tunnel junction layer disposed on an upper surface of the common contact layer
Implementation Method 2
When a bias is applied, the n-type semiconductor layer and the p-type semiconductor layer each carry electrons and holes to the active layer and light is emitted as the electrons and holes recombine radiatively in the active layer
Data Source
AI summary
A light emitting diode having multiple tunnel junctions is provided. This comprises the common contact layer, the first and second tunnel junction layers respectively disposed on the bottom surface and the upper surface of the common contact layer, the first light emitting structure disposed on the bottom surface of the first tunnel junction layer and the second light emitting structure disposed on the upper surface of the second tunnel junction layer. Light emitting structures emitting blue and green light may be disposed above and below the common contact layer. By injecting holes into the first light emitting structure and the second light emitting structure through the common contact layer formed of the n-type semiconductor, current spreading effect is improved, leading to improved light emitting efficiency. Since the n-type semiconductor layer can be disposed on the upper surface exposed to the outside, risk of damage occurring in subsequent fabrication steps can be reduced.