Light Emitting Device Recessed Low Refractive Index Electrode Absorption
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Solution Overview
Problem
In semiconductor light emitting devices, such as semiconductor lasers and LEDs, it is challenging to increase the light confinement factor due to limitations in the difference in refractive index between the active layer and the cladding layer, leading to light leakage towards the electrode, which results in absorption and loss.
Innovation Solution
A light emitting device with a laminated structure that includes a substrate, a first semiconductor layer, an active layer, and a second semiconductor layer, featuring recessed parts with a low refractive-index material lower than the second semiconductor layer, which reduces light leakage by lowering the average refractive index in the planar direction and minimizing electrode absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the difference in refractive index between the active layer and the cladding layer is increased to improve light confinement, then the light confinement factor is improved, but the material selection is limited due to lattice matching requirements
Solution Approach 1:
The patent introduces a recessed part with low refractive-index material (such as air or silicon oxide) at the specific location where light leakage occurs (between the active layer and electrode). This local modification of refractive index creates an optical barrier without requiring changes to the bulk material composition, thereby maintaining lattice matching while improving light confinement locally.
Solution Approach 2:
The recessed part acts as an intermediary optical layer between the active layer and the electrode. This intermediate structure with low refractive index prevents direct light leakage to the electrode, serving as a mediator that manages light propagation without requiring material changes to the semiconductor layers themselves.
2Reliability
If the thickness of the second semiconductor layer is increased to reduce light leakage, then light confinement is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of increasing the thickness of the second semiconductor layer uniformly, the patent segments the structure by introducing a localized recessed part. This segmentation allows light confinement to be achieved in the critical region near the electrode without increasing the overall layer thickness or complexity of the semiconductor stack.
Solution Approach 2:
The patent addresses the light leakage problem by moving from a vertical thickness adjustment approach to a lateral structural modification approach. The recessed part creates a horizontal/dimensional feature that affects light propagation without requiring increased vertical thickness of the semiconductor layers.
3Loss of energy
If a recessed part with low refractive-index material is introduced to reduce light absorption by the electrode, then light confinement is improved, but the device structure becomes more complex
Solution Approach 1:
The recessed part can be filled with low refractive-index material such as air (creating a porous or void structure) or silicon oxide. This porous or low-density material approach provides effective light confinement with minimal added material complexity and maintains compatibility with existing semiconductor manufacturing 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
The solution effectively reduces light absorption by the electrode, enhances light confinement, and decreases resistance in the second electrode, thereby improving the performance of the light emitting device without increasing the thickness of the second semiconductor layer.
Implementation Method 1
a recessed part is disposed on an opposite side to the substrate side of the laminated structure, the recessed part is provided with a low refractive-index part lower in refractive index than the second semiconductor layer
Data Source
AI summary
A light emitting device is provided that makes it possible to reduce absorption of light by an electrode. The light emitting device includes a substrate, and a laminated structure provided to the substrate, wherein the laminated structure includes a first semiconductor layer, a second semiconductor layer different in conductivity type from the first semiconductor layer, and an active layer disposed between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer is disposed between the substrate and the active layer, a recessed part is disposed at an opposite side to the substrate side of the laminated structure, the recessed part is provided with a low refractive-index part lower in refractive index than the second semiconductor layer, a depth of the recessed part is no larger than a distance between a surface at an opposite side to the substrate side of the laminated structure and the active layer, and an electrode is disposed at an opposite side to the substrate side of the laminated structure.