InGaN P-Type Injection Layer with AlGaInN Segmentation
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Solution Overview
Problem
The formation of a p-type injection layer in optoelectronic semiconductor structures, particularly in InGaN-based structures, is challenging due to lattice parameter mismatch with the active layer, leading to stress, cracks, and poor material quality, especially when the indium content is high or when forming a super lattice is complex and time-consuming.
Innovation Solution
A p-type injection layer comprising a first InGaN layer with a thickness of 50 nm to 300 nm, topped with a second layer of AlGaInN elemental layers, each less than critical relaxation thickness, forming a periodic structure with varying aluminum, indium, and gallium compositions to match the lattice parameter and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the p-type injection layer is made of GaN, then the lattice parameter mismatch with the active InGaN layer is reduced, but high stress and cracks occur in the injection layer
Solution Approach 1:
The p-type injection layer is divided into multiple thin AlGaInN elemental layers with varying compositions, each layer being thinner than the critical relaxation thickness. This segmentation allows the layer to accommodate lattice mismatch through compositional grading rather than creating high stress concentrations, thereby preventing cracks while maintaining lattice parameter compatibility with the InGaN active layer
Solution Approach 2:
The aluminum and indium compositions are varied across different elemental layers to gradually transition the lattice parameter from the substrate toward the active layer. This compositional parameter change enables the p-type injection layer to match the lattice parameter of the InGaN active layer while distributing stress uniformly, preventing crack formation
2Reliability
If the p-type injection layer consists of InGaN with indium concentration greater than 10% or 15%, then the material quality improves, but the formation temperature must be relatively low leading to poor material quality and high background concentration of donors
Solution Approach 1:
The patent employs AlGaInN composite material system instead of pure InGaN, allowing the p-type injection layer to achieve the required material quality with controlled donor concentrations. The aluminum and indium compositions are optimized to maintain good crystalline quality while enabling formation at temperatures that prevent excessive background donor concentrations
3Reliability
If the p-type injection layer is formed as a super lattice, then the average hole concentration is improved several times, but the structure becomes particularly complex and time-consuming to manufacture
Solution Approach 1:
The patent implements local quality variations within the p-type injection layer by creating elemental layers with different aluminum and indium compositions. Each local region (elemental layer) has optimized properties for hole concentration, while the overall structure remains simpler than a full super lattice. The compositional variations are confined to specific layers rather than requiring periodic modulation throughout the entire structure
Solution Approach 2:
Instead of implementing a complete super lattice structure with full periodic modulation, the patent applies partial action by using discrete elemental layers with varying compositions only where necessary to achieve the desired hole concentration. This partial implementation achieves the beneficial effect of increased hole concentration while avoiding the excessive complexity of a full super lattice structure
4Productivity
If the p-type injection layer is made thick to ensure sufficient current flow, then the current flow improves, but the formation of defects such as threading dislocations and V-pits increases
Solution Approach 1:
The patent varies the aluminum and indium composition parameters across different elemental layers to optimize the balance between thickness and defect formation. By adjusting these compositional parameters, the p-type injection layer can achieve sufficient thickness for good current flow while maintaining low defect density through compositional optimization that reduces strain accumulation
Data Source
AI summary
An optoelectronic semiconductor structure (SC) comprises an active InGaN-based layer disposed between an n-type injection layer and a p-type injection layer, the active p-type injection layer comprising a first InGaN layer and, disposed on the first layer, a second layer composed of a plurality of AlGaInN elemental layers, each elemental layer having a thickness less than its critical relaxation thickness, two successive elemental layers having different aluminum and/or indium and/or gallium compositions.