Patterned Semiconductor Substrates for Light Extraction and Epitaxy
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Solution Overview
Problem
Current semiconductor devices, particularly light-emitting diodes, face challenges in achieving high light extraction efficiency and external quantum efficiency due to defects and total internal reflection, which are not effectively addressed by existing technologies.
Innovation Solution
A semiconductor device with a substrate featuring holes of varying depths and distributions is used, where the buffer layer is epitaxially grown laterally over these holes, reducing defect density and enhancing epitaxy quality, and the substrate's refractive index differences help in suppressing total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flat substrate is used for growing semiconductor layers, then the manufacturing process is simple, but the light extraction efficiency is low due to total internal reflection
Solution Approach 1:
The substrate surface is modified with holes of varying depths and lateral expansions, creating a non-planar curved surface structure. This curvature disrupts the uniform interface between substrate and buffer layer, reducing total internal reflection and improving light extraction efficiency while maintaining a relatively simple manufacturing process through selective etching
Solution Approach 2:
The substrate is transformed into a porous structure with multiple holes penetrating through it. These pores create refractive index variations and scattering centers that reduce total internal reflection, allowing more light to be extracted from the semiconductor device while the porous structure can be formed using standard semiconductor processing techniques
2Ease of manufacture
If the substrate surface is made flat and uniform, then the epitaxial growth is easy to control, but defect density increases and epitaxy quality decreases
Solution Approach 1:
Instead of making the entire substrate surface uniform, the invention introduces localized variations through holes with different depths, diameters, and lateral expansions at different positions. This local non-uniformity creates favorable conditions for epitaxial growth by reducing defect formation at the interface, while the overall process remains controllable through systematic patterning
Solution Approach 2:
The substrate is pre-modified with a pattern of holes before epitaxial growth begins. This preliminary structuring of the substrate surface creates optimal conditions for subsequent buffer layer growth, allowing the epitaxial process to proceed with better quality and fewer defects from the outset
3Ease of manufacture
If holes of uniform depth are formed in the substrate, then the manufacturing process is simple, but light extraction efficiency is insufficient due to limited refractive index variation
Solution Approach 1:
The invention employs holes with asymmetric characteristics - varying depths, different diameters, and lateral expansions at different levels. This asymmetric structure creates more effective refractive index variations and light scattering compared to uniform holes, significantly improving light extraction efficiency. The added complexity is manageable through systematic fabrication processes
Solution Approach 2:
The hole structure is extended from a single-dimensional uniform depth to multi-dimensional variations including different depths, lateral expansions, and radial configurations. This dimensional complexity creates more effective optical scattering and refractive index variations, enhancing light extraction while the structures can be formed through sequential processing steps
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 approach improves the epitaxy quality of semiconductor layers and increases light extraction efficiency, leading to enhanced external quantum efficiency and performance in light-emitting devices.
Implementation Method 1
epitaxially forming a buffer layer on the upper surface, and after forming the buffer layer, the substrate includes a plurality of holes
Implementation Method 2
the substrate's refractive index differences help in suppressing total internal reflection
Implementation Method 3
the substrate's refractive index differences help in suppressing total internal reflection
Data Source
AI summary
A semiconductor device includes a substrate having an upper surface, a buffer layer formed on the upper surface, and an element structure formed on the buffer layer. The substrate includes a plurality of holes extending from the upper surface of the substrate to an inside of the substrate and forming a plurality of openings at the upper surface of the substrate. In a cross-sectional view of the semiconductor device, at least two of the holes have different depths.