Translucent Electrode Structure for Semiconductor Light Emitting Element
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Solution Overview
Problem
Conventional nitride semiconductor light emitting elements face issues with current spread uniformity, high resistance, increased voltage, and light absorption due to electrode materials, which hinder power efficiency and mass productivity, especially in high-power applications like illumination.
Innovation Solution
A light emitting element with a translucent electrode structure featuring a light transmissive first layer and a reflective second layer, where the first layer projects from both sides of the second layer in a cross-section, is arranged adjacent to the light emitting structure, reducing contact resistance and light absorption, and enhancing power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent conductive film is used for the n-electrode, then light transmission is improved, but current spread uniformity deteriorates and resistance increases
Solution Approach 1:
The electrode is divided into multiple segments: a transparent conductive film layer and a reflective metal layer that are partially superposed. The transparent conductive film provides light transmission while the reflective metal layer provides current spreading, and their partial overlap creates a segmented structure that combines both functions effectively
Solution Approach 2:
The electrode uses a composite structure combining transparent conductive film material (such as ITO) and reflective metal material (such as Al or Ag). This composite electrode structure integrates the light transmission property of the transparent conductive film with the current spreading capability of the reflective metal, resolving the contradiction between light transmission and current spread uniformity
2Reliability
If a metal layer/reflection layer is superposed on the transparent electrode, then current spread is improved, but light absorption increases
Solution Approach 1:
The reflective metal layer is not uniformly applied across the entire electrode area but is instead localized to specific regions where it is most needed for current spreading. The transparent conductive film remains exposed in areas where light transmission is critical, creating local quality variations that optimize both current spread and light transmission in different zones
Solution Approach 2:
Instead of fully covering the transparent electrode with a reflective metal layer (which would cause excessive light absorption), the invention applies the metal layer partially or excessively only where needed for current spreading. This partial action maintains light transmission in critical areas while providing sufficient current spreading in other areas
3Illumination intensity
If the n-electrode is lowered to suppress light shielding, then light extraction is improved, but electrode contact with the n-type layer deteriorates
Solution Approach 1:
The electrode structure transitions from a single-plane configuration to a multi-dimensional structure with vertical layering. The transparent conductive film and reflective metal layer are arranged in vertical layers with partial superposition, creating a three-dimensional electrode structure that maintains good contact with the n-type layer while allowing light to pass through the transparent portions
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 power efficiency, reduces driving voltage, and increases mass productivity while maintaining low cost, resulting in enhanced electric and optical characteristics for the light emitting device.
Implementation Method 1
a light transmissive first layer and a reflective second layer, wherein the first layer has projecting portions projected from both sides of the second layer
Data Source
AI summary
It is an important factor in application to the illumination field and the like to obtain a characteristic excellent in power efficiency in a light emitting element. The present invention provides a semiconductor light emitting element including: first and second conductive type semiconductor layers; first and second electrodes respectively provided on the same plane sides as the first and second conductive type semiconductor layers; and a light emitting structure, provided with the second electrode and including the first and second conductive type semiconductor layers, wherein the first electrode provided on an exposed surface of the first conductive type semiconductor layer at least has a translucent first layer and a reflective second layer, and the first layer has projecting portions projected from both sides of the second layer in a cross section of the element crossing over the light emitting structure and the first electrode.