Series-Connected Segmented LED on Silicon Substrate
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Solution Overview
Problem
Existing methods for fabricating series-connected light emitting diodes (LEDs) on non-insulating substrates like silicon wafers face challenges in electrical isolation and heat dissipation, limiting their efficiency and cost-effectiveness compared to LEDs grown on insulating substrates like sapphire.
Innovation Solution
A light source structure is created by bonding GaN semiconductor layers to a silicon substrate, using a barrier to electrically isolate segments and a mirror to improve efficiency, with series connection electrodes and a heat-conductive substrate for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If LEDs are connected in series to increase driving voltage and reduce current, then power losses are reduced and efficiency is improved, but heat dissipation becomes more challenging and manufacturing complexity increases
Solution Approach 1:
The LED array is divided into multiple segments with isolation regions between them, allowing each segment to be electrically isolated while maintaining series connection. This segmentation enables better heat management by distributing heat sources across multiple isolated regions on the substrate.
Solution Approach 2:
Isolation regions act as intermediary structures between LED segments, providing both electrical isolation and thermal management. These regions serve as mediators that allow series connection while preventing thermal accumulation and electrical interference between adjacent segments.
2Ease of manufacture
If LEDs are fabricated on silicon wafers instead of sapphire substrates, then manufacturing costs are reduced and ease of manufacture is improved, but electrical isolation between series-connected LEDs becomes more difficult
Solution Approach 1:
The silicon substrate is divided into isolation regions that electrically isolate adjacent LED segments. This segmentation approach enables the use of inexpensive silicon wafers while achieving the electrical isolation normally provided by sapphire substrates, thus reducing manufacturing costs without sacrificing electrical isolation performance.
Solution Approach 2:
The isolation regions are extracted as separate functional elements from the continuous silicon substrate. By removing or isolating specific regions of the substrate, electrical isolation between segments is achieved while maintaining the cost advantages of silicon wafer fabrication.
3Illumination intensity
If higher current is used to increase light output, then total light output increases, but conversion efficiency decreases and lifetime is reduced
Solution Approach 1:
The LED array is segmented into multiple series-connected units, allowing the total light output to be increased by adding more segments rather than increasing current through a single LED. This maintains optimal current levels for each individual LED while achieving higher overall illumination intensity.
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 approach allows for efficient series connection of LEDs on silicon substrates, improving light extraction and heat dissipation while reducing costs, achieving higher voltage operation with lower current and increased efficiency.
Implementation Method 1
The active layer emits light when holes and electrons from the outer layers combine in the active layer
Implementation Method 2
Heat dissipation often places a limit on the power level at which an LED operates
Implementation Method 3
A mirror is in electrical contact with the first layer in each of the segments
Data Source
AI summary
A light source and method for making the same are disclosed. The light source includes a conducting substrate, and a light emitting structure that is divided into segments. The light emitting structure includes a first layer of semiconductor material of a first conductivity type deposited on the substrate, an active layer overlying the first layer, and a second layer of semiconductor material of an opposite conductivity type from the first conductivity type overlying the active layer. A barrier divides the light emitting structure into first and second segments that are electrically isolated from one another. A serial connection electrode connects the first layer in the first segment to the second layer in the second segment. A power contact is electrically connected to the second layer in the first segment, and a second power contact electrically connected to the first layer in the second segment.