LED Intermediate Layer Roughness for Better Light Extraction
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Solution Overview
Problem
Existing light emitting diodes (LEDs) face challenges in achieving efficient light emission and heat dissipation, particularly with flip-chip-type LEDs, where light loss occurs at the P-electrode pad and current spreading is inefficient.
Innovation Solution
A light emitting device is designed with a specific structure including a first and second window layer, an active layer, electron and hole regulation layers, and an intermediate layer with different roughnesses on its upper and lower interfaces, which enhances lattice match and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective electrode is formed on the P-type semiconductor layer to prevent light loss, then light extraction efficiency is improved, but device complexity increases due to additional layers and processing steps
Solution Approach 1:
An intermediate layer is introduced between the P-type semiconductor layer and the window layer to serve as a mediator that prevents light absorption by the P-electrode pad. This intermediate layer has different roughnesses on its upper and lower interfaces, allowing it to fulfill multiple functions: improving light extraction efficiency while maintaining structural integrity and reducing the need for additional complex reflective electrode structures.
Solution Approach 2:
The intermediate layer exhibits local quality variations through different roughnesses at its upper and lower interfaces. The lower interface has higher roughness to scatter light and improve extraction efficiency, while the upper interface has lower roughness to maintain good optical coupling with the window layer. This localized differentiation allows the single intermediate layer to perform multiple functions without increasing overall device complexity.
2Illumination intensity
If the intermediate layer has different roughnesses on upper and lower interfaces, then light extraction efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The intermediate layer's performance is optimized by changing the roughness parameter at different interfaces. The lower interface is designed with higher roughness (e.g., RMS 5-50 nm) to scatter light effectively, while the upper interface has lower roughness (e.g., RMS 1-10 nm) for optimal optical coupling. These parameter variations are achieved through controlled growth conditions during epitaxial processing, allowing precise control of light extraction without requiring post-processing steps.
3Illumination intensity
If the intermediate layer thickness is optimized to be smaller than adjacent layers, then light extraction is improved, but the layer becomes more difficult to control during fabrication
Solution Approach 1:
The intermediate layer thickness is optimized to be smaller than the adjacent window layer and P-type semiconductor layer, with a thickness range of 1-10 micrometers. This thickness optimization balances light extraction efficiency (thinner layers allow better light transmission) with fabrication control (thinner layers are more challenging to grow uniformly). The specific thickness is adjusted based on the wavelength of emitted light and the specific device architecture to achieve optimal performance while remaining manufacturable.
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 proposed structure improves light extraction efficiency, prevents light absorption, and enhances heat dissipation, leading to a more reliable and efficient light emitting module.
Implementation Method 1
an intermediate layer interposed between the second window layer and the hole regulation layer, wherein the intermediate layer has different roughnesses on upper and lower interfaces thereof
Implementation Method 2
A light emitting diode (LED) is one of light emitting devices emitting light upon application of electric current thereto
Implementation Method 3
improving heat dissipation efficiency
Data Source
Figure 1~2
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AI summary
A light emitting device is disclosed. The light emitting device includes: a first window layer supplying electrons; a second window layer supplying holes; an active layer interposed between the first window layer and the second window layer; an electron regulation layer interposed between the first window layer and the active layer; a hole regulation layer interposed between the second window layer and the active layer; and an intermediate layer interposed between the second window layer and the hole regulation layer, wherein the intermediate layer has different roughnesses on upper and lower interfaces thereof.