Semiconductor Light-Emitting Layer Structure for Low-Reflection Output
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Solution Overview
Problem
Current semiconductor light-emitting devices face challenges in optimizing light output and luminous efficiency due to reflection and scattering of light at the substrate's back surface, particularly in the wavelength range of 900 to 1000 nm, where silicon photodiodes are sensitive.
Innovation Solution
The semiconductor light-emitting device is designed with a specific layered structure including a substrate, first and second semiconductor layers, and barrier layers with controlled energy bandgaps and refractive indices, optimized through epitaxial growth and mesa etching, to minimize light reflection and scattering, enhancing carrier confinement and luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional LED structure is used with standard substrate and semiconductor layers, then the device is simple to manufacture, but light reflection and scattering occur at the substrate back surface reducing light output and luminous efficiency
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Al composition ratio in the AlGaAs semiconductor layers and adjusting the thickness of each layer to optimize the refractive index gradient. This gradual refractive index transition from the active layer through intermediate layers to the substrate minimizes reflection and scattering, thereby improving light output and luminous efficiency without adding complex external optical components
Solution Approach 2:
The patent implements local quality by creating a layered structure where each layer has specifically tailored properties: the first AlGaAs layer has a higher Al composition ratio than the second layer, creating a refractive index gradient. The substrate back surface is treated with a specific refractive index material. Each layer's local optical properties are optimized to collectively reduce reflection and scattering throughout the light path
2Productivity
If the refractive index of the substrate is increased to reduce reflection, then light output improves, but the complexity of material selection and layer design increases
Solution Approach 1:
The patent uses parameter changes by systematically varying the Al composition ratio (x value) in AlGaAs layers and the thickness of each layer to achieve the desired refractive index gradient. The first AlGaAs layer has a higher Al composition ratio than the second layer, creating a controlled transition in refractive index that reduces reflection while maintaining a manageable layered structure
Solution Approach 2:
The patent employs composite materials by combining GaAs substrate with AlGaAs semiconductor layers of different compositions. The AlGaAs layers serve as intermediate optical layers with refractive indices between the GaAs substrate and air, creating a composite structure that gradually transitions the refractive index and minimizes reflection at interfaces
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 light output and luminous efficiency by suppressing light reflection and scattering, achieving maximum light output through controlled Al composition ratios and refractive index relationships between layers, thereby optimizing the emission in the desired wavelength range.
Implementation Method 1
The active layer includes at least one quantum well layer and a first barrier layer. The quantum well layer has a third energy bandgap narrower than the first and second energy bandgaps.
Implementation Method 2
The substrate has a refractive index greater than a refractive index of the first semiconductor layer at a wavelength of light radiated from the active layer. The refractive index of the first semiconductor layer is not less than a refractive index of the first barrier layer.
Data Source
AI summary
A semiconductor light-emitting device includes a substrate having a first energy bandgap, a first semiconductor layers on the substrate, an active layer on the first semiconductor layer, and a second semiconductor layer on the active layer. The active layer includes a quantum well layer, and a first barrier layer between the first semiconductor layer and the quantum well layer. The first semiconductor layer has a second energy bandgap wider than the first energy bandgap. The quantum well layer has a third energy bandgap narrower than the first and second energy bandgaps. The second semiconductor layer has a fourth energy bandgap wider than the third energy bandgap. The substrate has a refractive index greater than a refractive index of the first semiconductor layer. The refractive index of the first semiconductor layer is not less than a refractive index of the first barrier layer.