GaN LED Dual Reflecting Layer Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GaN-based LEDs suffer from low external quantum efficiency due to light absorption by the P-type layer and uneven current distribution, leading to reduced light-emitting efficiency and shortened service life.
Innovation Solution
A dual reflecting layer structure is introduced, comprising an annular reflecting layer and a metal reflecting layer between the LED epitaxial layer and the P electrode, which enhances light extraction efficiency by reflecting light sideways and upwards, and blocks current accumulation to improve uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a metal reflecting layer is used to extract light sideways, then light extraction efficiency is improved, but light absorption by the P electrode increases and service life is shortened
Solution Approach 1:
The reflecting structure is segmented into two distinct layers: an annular reflecting layer for sideways light extraction and a metal reflecting layer for upward light extraction. This segmentation allows each layer to perform its specific function without the harmful effects of the other, particularly preventing the P electrode from absorbing light while maintaining high light extraction efficiency
Solution Approach 2:
The annular reflecting layer acts as an intermediary between the light-emitting layer and the P electrode, extracting light sideways before it can be absorbed by the P electrode. This intermediary structure resolves the contradiction by providing a beneficial light extraction path without the harmful absorption effect
2Illumination intensity
If ITO layer is adopted as current spreading layer to enhance transmittance, then light transmittance is improved, but LED voltage increases and service life is shortened
Solution Approach 1:
The invention changes the electrical parameter (voltage) by optimizing the current spreading layer configuration and thickness, while maintaining the optical parameter (transmittance) through the dual reflecting layer structure. This allows achieving high light transmittance without the high voltage penalty
3Productivity
If conventional single reflecting layer structure is used, then device complexity is low, but light extraction efficiency is insufficient due to non-uniform current distribution
Solution Approach 1:
The reflecting structure is divided into two functional segments: an annular reflecting layer for lateral light extraction and a metal reflecting layer for upward light extraction. This segmentation enables each layer to address specific light extraction needs, improving overall efficiency while maintaining manageable structural complexity
Solution Approach 2:
Different regions of the LED structure are assigned different reflecting properties: the annular reflecting layer provides lateral reflection in specific zones, while the metal reflecting layer provides upward reflection in the central region. This local differentiation optimizes light extraction efficiency without requiring uniform complexity throughout the entire 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
The dual reflecting layer structure significantly improves light extraction efficiency and uniform current distribution, enhancing the overall light-emitting efficiency and extending the service life of GaN-based HBLEDs.
Implementation Method 1
the metal reflecting layer (typically, Al or Ag material) reflects part of light emitted by the light-emitting layer and extracts light sideways
Implementation Method 2
a reflecting structure that comprises an annular reflecting layer and a metal reflecting layer is formed between the P electrode and the epitaxial layer, wherein, the geometric center vertically corresponds to the P electrode
Data Source
AI summary
A GaN-based LED includes a substrate; an epitaxial layer over the substrate; a current spreading layer over a P-type layer; and a P electrode over the current spreading layer. The epitaxial layer includes the P-type layer, a light-emitting area, and an N-type layer. An annular reflecting layer and a metal reflecting layer are formed between the P electrode and the epitaxial layer. The geometric center vertically corresponds to the P electrode; the annular reflecting layer is formed between the current spreading layer and the P-type layer; the metal reflecting layer is formed between the current spreading layer and the P electrode; and a preset distance is arranged between the annular reflecting layer and the metal reflecting layer. The annular reflecting layer and the metal reflecting layer reduce light absorption of the P electrode and improve light extraction efficiency.