LED Light Extraction via Textured Semiconductor Cavities
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Solution Overview
Problem
Conventional light-emitting diode (LED) devices face a trade-off between high light extraction efficiency and lateral current conduction, as a textured surface enhances light extraction but decreases current spreading and increases forward voltage.
Innovation Solution
A light-emitting device design featuring a second conductivity type semiconductor layer with cavities, a transparent conductive oxide layer with both flat and textured portions, and a reflective metal layer to improve adhesion and current spreading while maintaining high light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a textured surface is formed on the semiconductor layer to enhance light extraction efficiency, then light extraction efficiency is improved, but lateral current conduction deteriorates and forward voltage increases
Solution Approach 1:
The patent applies local quality by creating distinct regions with different surface characteristics: a first region with a textured surface for high light extraction efficiency, and a second region with a flat surface for good current conduction. This allows each region to optimize its specific function without compromising the other, resolving the contradiction between light extraction and current conduction.
Solution Approach 2:
The semiconductor layer is segmented into multiple regions with different surface properties. The textured region and flat region are spatially separated, allowing the device to simultaneously achieve high light extraction in the textured region while maintaining good current conduction through the flat region. This segmentation strategy directly addresses the technical contradiction.
2Illumination intensity
If a textured surface is formed on the semiconductor layer to enhance light extraction efficiency, then light extraction efficiency is improved, but forward voltage increases
Solution Approach 1:
By creating a flat surface region alongside the textured region, the patent ensures good current conduction paths exist, which helps maintain lower forward voltage. The flat region compensates for the voltage increase that would otherwise result from the textured surface, allowing the device to achieve high light extraction without excessive forward voltage penalty.
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 solution effectively decreases impedance and forward voltage, enhancing lateral current conduction and overall efficiency while maintaining high light extraction efficiency.
Implementation Method 1
a first reflective metal layer formed between the first transparent conductive oxide layer and the first electrode
Implementation Method 2
a second conductivity type semiconductor layer formed on the light-emitting layer and comprising a first plurality of cavities such that an upper surface of the second conductivity type semiconductor layer is a textured surface
Data Source
AI summary
A light-emitting device, comprises a light-emitting stacked layer comprising a first conductivity type semiconductor layer; a light-emitting layer formed on the first conductivity type semiconductor layer; and a second conductivity type semiconductor layer formed on the light-emitting layer and comprising a first plurality of cavities; a first dielectric layer formed on a first part of the second conductivity type semiconductor layer; a first transparent conductive oxide layer formed on the first dielectric layer and on a second part of the second conductivity type semiconductor layer, the first transparent conductive oxide layer including a first portion in contact with the first dielectric layer and including a second portion in contact with the upper surface of the second conductivity type semiconductor layer; a first electrode formed on the first portion; and a first reflective metal layer formed between the first transparent conductive oxide layer and the first electrode.