Trapezoidal Protrusion Electrode for Light Extraction
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Solution Overview
Problem
Light-emitting devices with planar nitride-based semiconductor layers face reduced light extraction efficiency due to light re-reflection and absorption by metal wiring electrodes, which impede the emission of light.
Innovation Solution
A light-emitting device design featuring a substrate with nitride-based semiconductor layers, an insulating layer, and a protrusion with a trapezoidal cross-section, where the transparent conductive layer covers the top surface and the electrode only partially covers the inclined surfaces of the protrusion, directing re-reflected light for extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metal wiring electrode with high reflectivity is used to minimize light absorption, then light reflection is improved, but light re-absorption by the electrode increases, reducing light extraction efficiency
Solution Approach 1:
The patent introduces a protrusion structure that adds vertical dimensionality to the electrode configuration. The electrode is positioned on the protrusion rather than directly on the flat substrate, creating a stepped structure that separates the electrode from the light-emitting region in the vertical direction, thereby reducing light re-absorption while maintaining reflectivity.
Solution Approach 2:
The protrusion structure acts as an intermediary element between the light-emitting semiconductor layer and the metal electrode. This intermediate structure allows the electrode to be positioned closer to the light-emitting region for better electrical connection while preventing direct contact that would cause light re-absorption, thus mediating between electrical connectivity and optical performance.
2Ease of manufacture
If a flat electrode structure is used for simple manufacturing, then device complexity is reduced, but light extraction efficiency deteriorates due to light re-reflection
Solution Approach 1:
The electrode structure is segmented into two distinct parts: a bottom electrode layer positioned on the protrusion and a top electrode layer positioned on the transparent conductive oxide. This segmentation allows each layer to perform its specific function optimally - the bottom layer provides reflectivity and electrical connection, while the top layer ensures uniform light emission - thereby improving light extraction efficiency while maintaining manufacturing feasibility through standard layer-by-layer fabrication processes.
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 by minimizing light re-absorption, resulting in improved luminance characteristics, with experimental verification showing a 2% increase in luminance compared to devices with flat electrode structures.
Implementation Method 1
a transparent conductive layer covering a top surface of the light-emitting structure, a top surface of the insulating layer, and the top surface of the protrusion
Implementation Method 2
an electrode covering at least one of inclined surfaces of the protrusion on the transparent conductive layer
Data Source
AI summary
A light-emitting device includes: a substrate; a light-emitting structure including first and second nitride-based semiconductor layers on the substrate and an active layer between the first and second nitride-based semiconductor layers; an insulating layer on a top surface of the light-emitting structure; a protrusion on the insulating layer, a top surface of the protrusion being larger than a bottom surface thereof, the protrusion having a trapezoidal cross-section; a transparent conductive layer covering a top surface of the light-emitting structure, a top surface of the insulating layer, and the top surface of the protrusion and having a constant thickness along the top surface of the light-emitting structure, the top surface of the insulating layer, and the top surface of the protrusion; and an electrode covering at least one of inclined surfaces of the protrusion on the transparent conductive layer.