Nitride Semiconductor Structure With V-Shape Cracks For Stress Relief
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Solution Overview
Problem
Nitride semiconductor structures face lattice dislocation and thermal stress issues during epitaxy due to lattice constant and thermal expansion coefficient mismatches, leading to cracking and reduced work efficiency, particularly in light-emitting diodes (LEDs).
Innovation Solution
A nitride semiconductor structure is designed with a substrate, first and second type nitride semiconductor layers, and multiple quantum well structures, where a higher concentration of a second type dopant in the second barrier layers or heavily doped layers creates V-shape cracks that allow stress release, improving epitaxy quality and light-emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitride semiconductor structure is formed using conventional epitaxy process, then the structure can be manufactured with standard工艺流程, but lattice dislocation and thermal stress occur due to mismatch between semiconductor layer and substrate, leading to cracking and reduced work efficiency
Solution Approach 1:
The active layer is divided into multiple quantum well structures (first and second multiple quantum well structures) with different compositions and functions. The first multiple quantum well structure contains quantum wells for light emission, while the second multiple quantum well structure serves as a stress relief layer with higher aluminum content, segmenting the stress distribution and preventing catastrophic cracking
Solution Approach 2:
Different regions of the semiconductor structure are assigned different compositions and properties. The second multiple quantum well structure has higher aluminum content specifically in regions where stress relief is needed, while the first multiple quantum well structure maintains optimal composition for light emission. This local differentiation allows simultaneous stress management and high-performance light emission
2Ease of manufacture
If the semiconductor layer is grown directly on the substrate, then the fabrication process is simplified, but thermal expansion coefficient mismatch causes serious bending and cracking
Solution Approach 1:
A second multiple quantum well structure is introduced as an intermediary layer between the substrate and the first multiple quantum well structure. This intermediate layer acts as a buffer that gradually transitions the stress from the substrate, preventing direct stress transmission that would cause bending and cracking while maintaining fabrication simplicity
3Reliability
If the quantum well structure is designed for high light-emitting efficiency, then the device performance is improved, but the structure becomes more sensitive to stress and cracking
Solution Approach 1:
The quantum well structure is segmented into two distinct multiple quantum well structures with different functions. The first multiple quantum well structure is optimized for light emission with appropriate quantum well thickness and composition, while the second multiple quantum well structure is designed with higher aluminum content specifically to handle stress, allowing each segment to perform its specialized function without compromise
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 structure effectively reduces stress and enhances light-emitting efficiency by allowing the first multiple quantum well structure to fill into V-shape cracks, improving the overall performance of nitride semiconductor devices.
Implementation Method 1
an issue of thermal stress can also occur due to mismatch of the thermal expansion coefficient (CTE)
Implementation Method 2
a lattice dislocation may easily occur during epitaxy process of semiconductor
Data Source
AI summary
A nitride semiconductor structure including a substrate, a first type nitride semiconductor layer disposed on the substrate, an active layer disposed between the substrate and the first type nitride semiconductor layer and a second type nitride semiconductor layer disposed between the substrate and the active layer is provided. The active layer includes a first multiple quantum well structure including a plurality of first quantum well layers and a plurality of first barrier layers staggered with each other, and a second multiple quantum well structure including a plurality of second quantum well layers and a plurality of second barrier layers staggered with each other. A second type dopant is doped into at least one of the second barrier layers, and a concentration of the second dopant in the second barrier layer is higher than that of the second dopant in the second type nitride semiconductor layer.