Dual-Stack Light-Emitting Device with Reflector and Protecting Layer
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Solution Overview
Problem
Conventional light-emitting devices face challenges in efficiently emitting multiple wavelengths simultaneously due to the complexity of layer formation and the need for flipping substrates during epitaxial growth, which increases manufacturing steps and can lead to light absorption issues.
Innovation Solution
A light-emitting device design featuring a first and second light-emitting semiconductor stack with a Distributed Bragg reflector and a protecting layer, where each stack emits radiation of different wavelengths, and the use of epitaxial growth to form layers directly on a shared substrate, reducing manufacturing steps and light absorption by optimizing contact layer thickness and doping concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional methods are used to emit multiple wavelengths simultaneously, then multiple light sources are required, but device complexity increases
Solution Approach 1:
The patent combines multiple light-emitting semiconductor stacks (first stack emitting first wavelength, second stack emitting second wavelength) into a single integrated device structure. The stacks are formed on a common substrate with shared electrodes and encapsulation, merging multiple wavelength-emitting functions into one device rather than using separate light sources, thereby reducing overall device complexity while maintaining multi-wavelength capability
Solution Approach 2:
The single light-emitting device structure performs multiple functions by emitting different wavelengths simultaneously through different semiconductor stacks. The common substrate, electrodes, and encapsulation layers serve universal purposes for both wavelength emissions, making the device multi-functional rather than requiring separate specialized components for each wavelength
2Adaptability or versatility
If substrates are flipped during epitaxial growth to form multiple stacks, then manufacturing steps increase, but layer formation flexibility improves
Solution Approach 1:
Instead of forming multiple semiconductor stacks by flipping the substrate in the vertical direction (requiring multiple epitaxial growth cycles), the patent forms the stacks simultaneously in the horizontal plane on different regions of the same substrate surface. This spatial arrangement in another dimension eliminates the need for substrate flipping and reduces manufacturing steps while maintaining the ability to create different layer structures for different wavelengths
3Object-affected harmful factors
If contact layers are made thicker to reduce light absorption, then electrical conductivity decreases, but light transmission improves
Solution Approach 1:
The patent optimizes the contact layer thickness to a specific parameter range that balances two competing requirements: the layer is thick enough to provide adequate electrical conductivity for reliable device operation, but thin enough to minimize light absorption and maximize light transmission. This precise parameter control resolves the contradiction between electrical performance and optical performance
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 design allows for efficient emission of multiple wavelengths with reduced manufacturing complexity and light absorption, enabling a compact, monolithic device suitable for applications like pulse oximeters, with independently controllable light-emitting stacks.
Implementation Method 1
the first active layer emits a first radiation of a first wavelength, and the second active layer emits a second radiation of a second wavelength
Implementation Method 2
a reflector between the first light-emitting semiconductor stack and the second light-emitting semiconductor stack
Data Source
AI summary
A light-emitting device comprises a first light-emitting semiconductor stack comprising a first active layer; a second light-emitting semiconductor stack below the first light-emitting semiconductor stack, wherein the second light-emitting semiconductor stack comprises a second active layer; a reflector between the first light-emitting semiconductor stack and the second light-emitting semiconductor stack; a protecting layer between the reflector and the second light-emitting semiconductor stack; and wherein the first light-emitting semiconductor stack further comprises a first semiconductor layer and a second semiconductor layer sandwiching the first active layer, the second light-emitting semiconductor stack further comprises a third semiconductor layer and a fourth semiconductor layer sandwiching the second active layer, wherein the second semiconductor layer has a first band gap, the third semiconductor layer has a second band gap, and the protecting layer has a third band gap between the first band gap and the second band gap.