Nitride Semiconductor Buffer Layer Stress Tuning
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Solution Overview
Problem
Conventional deep UV LEDs with aluminum nitride (AlN)-based buffer layers experience high compressive stress due to lattice mismatch, leading to increased dislocation density and reduced luminous efficiency.
Innovation Solution
A nitride-based semiconductor device with a three-dimensional stress tuning layer formed on the buffer layer, which cooperatively defines an interface with the buffer layer, featuring a composition distribution that allows for stress release and improved lattice quality, comprising a substrate, buffer layer, three-dimensional stress tuning layer, n-type semiconductor layer, active layer, and p-type semiconductor layer grown using MOCVD techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an AlN-based buffer layer is used in conventional deep UV LEDs, then the device structure is simple and manufacturing is easier, but high compressive stress occurs due to lattice mismatch, leading to increased dislocation density and reduced luminous efficiency
Solution Approach 1:
The buffer layer is divided into multiple sub-layers with different compositions (AlN, AlGaN with varying Ga content) arranged in a segmented structure. This segmentation allows progressive stress management while maintaining manufacturing feasibility, resolving the contradiction between ease of manufacture and luminous efficiency by creating intermediate layers that gradually transition the lattice structure.
Solution Approach 2:
Different regions of the buffer layer are assigned different aluminum and gallium compositions to create local variations in stress characteristics. The local quality principle is applied by optimizing the composition at each interface to minimize dislocation density locally, which collectively improves overall luminous efficiency while maintaining a manufacturable structure.
2Device complexity
If an AlN-based buffer layer is used in conventional deep UV LEDs, then the device structure is simple, but high compressive stress occurs due to lattice mismatch, leading to increased dislocation density
Solution Approach 1:
The buffer layer is segmented into multiple sub-layers with progressively varying compositions, which manages lattice mismatch through staged transitions. This segmentation improves manufacturing precision by reducing dislocation density at each interface while keeping the overall device complexity manageable through a systematic multi-layer approach.
Solution Approach 2:
The invention transitions from a conventional single-layer buffer structure to a multi-dimensional composition distribution within the buffer layer. By introducing compositional variation in multiple dimensions (depth and lateral composition gradients), the patent achieves superior lattice quality control without excessively increasing device complexity.
3Stress or pressure
If high compressive stress is experienced by AlGaN-based layers, then the conventional AlN-based buffer layer structure is maintained, but dislocation density increases and lattice quality deteriorates
Solution Approach 1:
The patent introduces layers with tensile stress characteristics to counterbalance the compressive stress in AlGaN-based layers. By strategically positioning layers with opposite stress properties, the net stress on sensitive layers is reduced, thereby improving lattice quality and reducing dislocation density while maintaining the overall buffer layer structure.
Solution Approach 2:
The invention systematically changes compositional parameters (aluminum and gallium content) across different buffer layer sub-layers to modulate stress characteristics. By adjusting these parameters, the patent optimizes the stress state at each interface to minimize dislocation formation and improve lattice quality without compromising the fundamental buffer layer function.
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 solution effectively reduces dislocation density and enhances luminous efficiency by managing stress through a three-dimensional composition distribution at the interface, improving the performance of deep UV LEDs.
Implementation Method 1
The three-dimensional stress tuning layer and the buffer layer cooperatively define an interface therebetween. The interface has a three-dimensional composition distribution.
Data Source
AI summary
A nitride based semiconductor device including a buffer layer, a three-dimensional stress tuning layer formed on the buffer layer, a first-type semiconductor layer formed on the three-dimensional stress tuning layer, an active layer formed on the first-type semiconductor layer, and a second-type semiconductor layer formed on the active layer. The three-dimensional stress tuning layer and the buffer layer cooperatively define an interface therebetween. The interface has a three-dimensional composition distribution.