Vertical Cavity LED Reflector Strain Management
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Solution Overview
Problem
The formation of semiconductor multi-layer reflectors for vertical cavity light-emitting devices often results in cracks due to strain between films with different compositions, leading to inadequate reflectance and decreased productivity due to increased production time and complexity.
Innovation Solution
A method involving a semiconductor substrate with a hexagonal crystal structure and a line mask extending along specific directions to grow high and low refractive index semiconductor films alternately, reducing strain and crack formation by controlling the growth regions, thereby forming high-quality reflectors with improved reflectance using fewer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If semiconductor films with different compositions are grown to obtain refractive index difference, then reflectance is improved, but strain is generated between films leading to cracks in the multi-layer film
Solution Approach 1:
The patent changes the compositional parameters of the semiconductor films systematically. The first semiconductor film has composition InxGa1-xN where 0 ≤ x ≤ 0.3, and the second semiconductor film has composition InyGa1-yN where 0.3 < y ≤ 1. By carefully controlling the indium composition range, the patent achieves sufficient refractive index difference for high reflectance while limiting compositional extremes that would generate excessive strain and cause cracks.
2Manufacturing precision
If the number of layered semiconductor films is increased to improve reflectance, then reflectance is improved, but productivity deteriorates due to increased production time
Solution Approach 1:
The patent optimizes the layer structure parameters by alternating between two specific film types with controlled thicknesses. The first semiconductor film thickness is 5-50 nm and the second semiconductor film thickness is 50-200 nm. This parameter optimization allows achieving the desired reflectance with a reduced number of layers compared to conventional designs, thereby shortening production time while maintaining high reflectance performance.
3Productivity
If thin films with large refractive index difference are employed to reduce the number of layers, then productivity is improved, but film quality deterioration occurs
Solution Approach 1:
The patent employs a composite material structure consisting of alternating layers of InxGa1-xN and InyGa1-yN semiconductor films. This composite structure combines materials with different indium compositions to achieve large refractive index difference while maintaining film quality. The specific composition ranges and thickness control ensure that each layer maintains high quality without defects, enabling the use of fewer layers to achieve the desired reflectance.
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 effectively reduces crack formation and enhances the quality and productivity of semiconductor multi-layer reflectors, achieving desired reflectance with fewer layers and improving emission consistency across multiple light-emitting segments.
Implementation Method 1
a first reflector formed on an exposed region exposed from the line mask on the c-plane of the semiconductor substrate, the first reflector comprising a high refractive index semiconductor film and a low refractive index semiconductor film having a refractive index smaller than that of the high refractive index semiconductor film, the high refractive index semiconductor film and the low refractive index semiconductor film being alternately layered
Implementation Method 2
a reflector formed from a semiconductor multi-layer film... alternately layering two thin films having refractive indices different from each other
Data Source
AI summary
A vertical cavity light-emitting device includes: a semiconductor substrate having a hexagonal crystal structure; a line mask extending linearly along at least one of a [11-20] direction and directions equivalent to the [11-20] direction on a c-plane of the semiconductor substrate; a first reflector provided on an exposed region exposed from the line mask on the c-plane of the semiconductor substrate, the first reflector comprising a high refractive index semiconductor film and a low refractive index semiconductor film having a refractive index smaller than that of the high refractive index semiconductor film, the high refractive index semiconductor film and the low refractive index semiconductor film being alternately layered; a light-emitting structure layer provided on the first reflector; and a second reflector disposed on the light-emitting structure layer so as to be opposed so the first reflector.