Semiconductor Light-Emitting Layer Structure for Backside Light Extraction
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Solution Overview
Problem
Semiconductor light-emitting devices face challenges in optimizing light output and luminous efficiency due to reflection and scattering of light at the back surface of the substrate, 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 layer structure including a substrate, first and second semiconductor layers, and barrier layers with controlled energy bandgaps and refractive indices to minimize light reflection and scattering, enhancing carrier confinement and luminous efficiency. This structure includes quantum well layers and barrier layers made of indium gallium arsenide and aluminum gallium arsenide phosphide, optimized through epitaxial growth and mesa etching to suppress crystal defects and improve light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional LED structure is used, then the device is simple to manufacture, but light reflection and scattering occur at the back surface of the substrate, reducing light output and luminous efficiency
Solution Approach 1:
The device is divided into multiple functional layers including a substrate, light-emitting layer, and multiple semiconductor layers with different conductivity types. This segmentation allows each layer to be optimized for specific functions, improving light extraction while maintaining manufacturability through standardized layer fabrication processes.
Solution Approach 2:
Different regions of the device have different properties: the substrate has specific refractive index characteristics, the light-emitting layer contains quantum wells for light generation, and the semiconductor layers have alternating conductivity types. This local differentiation optimizes light extraction at the back surface while maintaining overall device performance.
2Device complexity
If a conventional LED structure is used, then the device structure is simple, but light scattering at the back surface reduces luminous efficiency
Solution Approach 1:
The multiple semiconductor layers with alternating conductivity types create continuous carrier confinement regions that guide light generation and extraction continuously through the device structure. This continuous action reduces energy loss from scattering while maintaining a relatively simple overall device architecture.
Solution Approach 2:
The device uses composite material structures with layers of different conductivity types and refractive indices. This composite approach optimizes light extraction by creating refractive index gradients that reduce scattering, thereby improving luminous efficiency without significantly increasing device complexity.
3Ease of manufacture
If the refractive index of the substrate is not optimized, then the manufacturing process is simpler, but reflection at the back surface reduces light extraction
Solution Approach 1:
The substrate is specifically selected or designed to have a refractive index higher than the first semiconductor layer at the operating wavelength. This parameter optimization reduces reflection at the back surface interface, improving light extraction while maintaining compatibility with standard 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 optimized layer structure significantly enhances light output and luminous efficiency by reducing reflection and scattering, achieving improved carrier confinement and increased light extraction through the back surface of the substrate, thereby improving the performance of the semiconductor light-emitting device.
Implementation Method 1
The active layer includes at least one quantum well 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.