Semiconductor Superlattice Buffer for Defect and Dopant Blocking
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Solution Overview
Problem
Current semiconductor devices face limitations in enhancing charge carrier mobility and reducing defects, particularly in heteroepitaxial growth, where lattice mismatch and dislocation defects lead to performance degradation and dopant diffusion issues.
Innovation Solution
The introduction of impurity and point defect blocking superlattice layers, composed of stacked semiconductor and non-semiconductor monolayers, between the substrate and buffer layers, and between the buffer and active layers, using silicon and germanium, to reduce effective mass and enhance mobility, while preventing dopant diffusion and defect propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heteroepitaxial growth is used to grow semiconductor layers on mismatched substrates, then device performance can be enhanced through material composition control, but lattice mismatch and dislocation defects lead to performance degradation
Solution Approach 1:
The patent introduces a superlattice buffer layer as an intermediary between the substrate and the active semiconductor layers. This superlattice structure acts as a mediator that gradually transitions from the substrate lattice to the epitaxial layer lattice, reducing the abrupt mismatch and preventing dislocation propagation into the active device regions.
Solution Approach 2:
The buffer layer is segmented into multiple thin alternating layers of different semiconductor materials with varying lattice constants. This segmentation creates a graded transition zone that distributes the lattice mismatch stress across multiple interfaces rather than concentrating it at a single boundary, thereby reducing dislocation formation.
2Reliability
If conventional buffer layers are used in heteroepitaxial growth, then defect reduction is achieved, but dopant diffusion still occurs causing performance degradation
Solution Approach 1:
The patent employs a composite superlattice buffer layer composed of alternating layers of different semiconductor materials (e.g., SiGe and Si). This composite structure creates multiple interfaces that act as barriers to dopant diffusion, while maintaining the mechanical compliance needed to reduce dislocation density. The different materials provide both structural support and diffusion blocking functionality.
3Speed
If strained material layers are introduced to enhance carrier mobility, then device speed and power performance improve, but additional fabrication complexity is introduced
Solution Approach 1:
The patent introduces strain into the semiconductor layers by controlling the composition and thickness of the superlattice buffer layers. By adjusting parameters such as the germanium content in SiGe layers and the thickness ratios of alternating layers, the patent creates controlled tensile or compressive strain that modifies the band structure and enhances carrier mobility without requiring complex post-growth processing.
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 results in higher charge carrier mobility, reduced defect density, and improved device performance by lowering conductivity effective mass and acting as a barrier to dopant diffusion, thereby enhancing the conductive properties and reducing unwanted scattering effects.
Implementation Method 1
a first impurity and point defect blocking superlattice layer between and in contact with the substrate and the buffer layer; and a second impurity and point defect blocking superlattice layer between and in contact with the buffer layer and the active layer
Implementation Method 2
The introduction of impurity and point defect blocking superlattice layers, composed of stacked semiconductor and non-semiconductor monolayers, between the substrate and buffer layers, and between the buffer and active layers, using silicon and germanium, to reduce effective mass and enhance mobility
Implementation Method 3
impurity and point defect blocking superlattice layers
Data Source
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AI summary
A semiconductor device may include a substrate (101) including a first Group IV semiconductor having a recess therein, an active layer (105) comprising a Group lll-V semiconductor within the recess, and a buffer layer (104) between the substrate and active layer and comprising a second Group IV semiconductor. The semiconductor device further includes an impurity and point defect blocking superlattice layer (125a, 125b) adjacent the buffer layer (104).