LED Active Layer Segmentation for Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The extraction efficiency of light emitted by a light emitting device is affected by the thickness of its active layer, where layers thicker than a certain wavelength lead to uniform constructive and destructive interference conditions, reducing efficiency and increasing leakage current, while thinner layers improve interference but compromise reliability.
Innovation Solution
A light emitting device structure is introduced with a thicker active layer than the effective wavelength, featuring a second active layer that emits light on a reflective layer and a first active layer that does not, with the distance between the reflective layer and the second active layer satisfying a constructive interference condition to maximize luminous efficiency without compromising reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the active layer is made thinner to improve interference effect and extraction efficiency, then extraction efficiency is improved, but reliability deteriorates due to increased leakage current
Solution Approach 1:
The active layer is divided into multiple quantum well layers (first active layer, second active layer, third active layer) with different thicknesses and positions. The second active layer is positioned at a distance from the reflective mirror satisfying constructive interference condition, while the first and third active layers are positioned elsewhere. This segmentation allows different portions of the active layer to serve different functions: the second active layer optimizes extraction efficiency through interference effect, while the overall multi-layer structure maintains reliability by distributing stress and reducing leakage current paths.
2Reliability
If the active layer is made thicker than wavelength/n, then reliability is improved, but extraction efficiency deteriorates as constructive and destructive conditions become uniformly distributed
Solution Approach 1:
Different regions of the active layer are given different qualities and functions. The second active layer is specifically positioned at a distance from the reflective mirror that satisfies the constructive interference condition (d = (2m+1)λ/4n), creating a local region of high extraction efficiency. The first and third active layers are positioned at different distances, creating regions with different interference characteristics. This local quality differentiation allows the structure to achieve both high extraction efficiency at critical locations and overall reliability through the distributed multi-layer configuration.
3Loss of energy
If a reflective mirror is introduced to improve extraction efficiency through interference effect, then extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The reflective mirror function is merged with the electrode structure. The second electrode layer serves dual purposes: providing electrical connection and acting as a reflective mirror for light extraction. This integration eliminates the need for a separate reflective mirror component, reducing device complexity while maintaining the interference effect for improved extraction efficiency. The electrode layer is positioned to satisfy the constructive interference condition with the second active layer, achieving both electrical and optical functions in a single structure.
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 maintains the existing interference effect while enhancing luminous efficiency and reducing leakage current, ensuring reliable operation by optimizing the active layer's thickness and emission characteristics.
Implementation Method 1
a distance between the reflective layer and the second active layer satisfies a constructive interference condition
Implementation Method 2
a second electrode layer including a reflective layer under the second conductive semiconductor layer
Data Source
AI summary
A light emitting device, a light emitting device package, and a lighting system are provided. The light emitting device includes: a second conductive semiconductor layer; an active layer over the second conductive semiconductor layer; a first conductive semiconductor layer over the active layer; and a second electrode layer including a reflective layer under the second conductive semiconductor layer. The active layer includes a second active layer that actually emits light on the reflective layer and a first active layer that does not emit light on the second active layer. A distance between the reflective layer and the second active layer satisfies a constructive interference condition.