Germanium Photodetector on Silicon via Trench Cladding
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Solution Overview
Problem
Conventional photodetectors face challenges in integrating a germanium layer on a silicon substrate due to lattice constant mismatch, leading to high treading dislocation density and increased leakage current, and are not economical for integration with CMOS ICs on a single substrate.
Innovation Solution
A method involving a bulk silicon substrate with a trench filled with cladding material, forming a single-crystallized silicon layer, and then a germanium layer, using insulating layers and high-temperature processing to reduce dislocation density and integrate with CMOS ICs economically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a germanium layer is grown on a single-crystalline silicon layer using an SOI substrate, then the photodetector can operate at 1.3-1.5 μm wavelength band, but the lattice constant mismatch causes high treading dislocation density and increased leakage current
Solution Approach 1:
The patent divides the germanium layer into multiple thin sub-layers (first germanium layer, second germanium layer, third germanium layer) with intermediate silicon nitride layers between them. This segmentation reduces the strain accumulation in each individual germanium sub-layer, thereby reducing treading dislocation density while maintaining the overall photodetector functionality at 1.3-1.5 μm wavelength band
Solution Approach 2:
The patent introduces silicon nitride layers as intermediary buffer layers between the silicon substrate and germanium layers, and between multiple germanium layers. These intermediary layers act as strain management interfaces that reduce the lattice mismatch stress, preventing dislocation propagation and reducing treading dislocation density
2Object-generated harmful factors
If conventional methods are used to minimize treading dislocation through post heat-treatment or temperature-varying CVD, then dislocation density is reduced, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent performs preliminary strain management by introducing silicon nitride buffer layers and segmenting the germanium structure during the deposition process itself, rather than requiring post-growth heat treatment or complex temperature-varying CVD processes. This preliminary structural design inherently reduces dislocation density without adding manufacturing complexity
3Manufacturing precision
If an SOI substrate is used for photodetector manufacturing, then single-crystal germanium growth is enabled, but the substrate cost increases and integration with CMOS ICs on one substrate becomes difficult
Solution Approach 1:
The patent uses silicon nitride layers as intermediary buffer structures that enable high-quality germanium growth on standard silicon substrates without requiring expensive SOI substrates. These intermediary layers manage the lattice mismatch stress, allowing single-crystal-like germanium quality to be achieved on cost-effective standard silicon substrates that are compatible with CMOS IC integration
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 approach effectively lowers treading dislocation density and enables economical integration of photodetectors with CMOS ICs on a single substrate, improving light absorptance and reducing manufacturing costs.
Implementation Method 1
The cladding material may have a lower refractive index than silicon
Implementation Method 2
forming an amorphous silicon layer and single-crystallizing the amorphous silicon layer
Implementation Method 3
forming a germanium layer on the single-crystallized silicon layer
Data Source
AI summary
A method of manufacturing a photodetector structure is provided. The method includes forming a structural layer by making a trench in a bulk silicon substrate and filling the trench with a cladding material, forming a single-crystallized silicon layer on the structural layer, and forming a germanium layer on the single-crystallized silicon layer.