GeSn Light Source Lateral Epitaxial Growth
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Solution Overview
Problem
The existing methods for producing germanium-tin (GeSn) light sources face challenges such as high through dislocation rates and mechanical stress, which reduce emission efficiency and introduce non-radiative recombinations, particularly when integrated with silicon-based substrates.
Innovation Solution
A method involving lateral epitaxial growth to form a base layer of GeSn or indium phosphide (InP) directly on a substrate, reducing through dislocations and mechanical stress, and optimizing the crystalline quality of the active zone by controlling the growth direction and thickness to enhance emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GeSn is epitaxially grown on Ge-VS from a germanium layer, then the light source can be manufactured with direct bandgap emission capability, but through-dislocations propagate vertically from the Ge/GeSn interface through the GeSn, reducing emission efficiency
Solution Approach 1:
The patent transitions from vertical epitaxial growth to lateral epitaxial growth of GeSn on Ge-VS. By growing the GeSn layer laterally from the sidewalls of the Ge layer rather than vertically from the top surface, the method prevents through-dislocations from propagating through the active region, as dislocations tend to form at the interface but are confined to the lateral growth front rather than extending vertically through the layer.
Solution Approach 2:
Instead of growing GeSn vertically from the Ge layer top surface (conventional approach), the patent inverts the growth direction by forming GeSn laterally from the Ge layer sidewalls. This inversion of the growth geometry fundamentally changes the dislocation propagation path and confines defects to the interface region rather than allowing them to extend through the entire GeSn layer.
2Reliability
If the GeSn alloy is grown with compressive mechanical stress to maintain direct bandgap, then the band gap remains direct for lower tin concentrations, but increasing tin concentration to compensate for compression induces crystal defects and non-radiative recombination
Solution Approach 1:
The patent changes the growth parameter from vertical to lateral epitaxial growth, which fundamentally alters the stress distribution and dislocation dynamics in the GeSn layer. Lateral growth allows for better stress management and reduces the formation of crystal defects even at higher tin concentrations, enabling the material to maintain direct bandgap properties without excessive defect formation.
3Reliability
If complex hybridization technologies are used to transfer III-V materials onto silicon, then light source functionality is achieved, but the manufacturing process becomes complex and not fully compatible with CMOS technologies
Solution Approach 1:
The patent uses homogeneous Ge-Sn alloy materials that can be grown directly on silicon substrates using standard CMOS-compatible epitaxial techniques, eliminating the need for complex hybridization processes required for III-V materials. The entire structure can be fabricated using silicon-based工艺流程, ensuring full CMOS compatibility while maintaining light source functionality.
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 method results in a GeSn-based light source with improved crystalline quality, reduced dislocation rates, and lower residual compressive stress, leading to enhanced emission efficiency and the ability to operate at room temperature with a lowered laser emission threshold.
Implementation Method 1
form a base layer by lateral growth, from at least one lateral germination face, of a third material, different from the first and second materials and preferably based on the third material, from at least one lateral germination face
Data Source
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AI summary
The invention relates to a method for producing a light source comprising a GeSn active zone sandwiched between two contact zones. The active zone is formed directly on a silicon oxide layer by a first lateral epitaxial growth of a Ge nucleation layer followed by a second lateral epitaxial growth of a GeSn base layer. Advantageously, a cavity is formed between the contact zones by encapsulation and etching to guide these lateral growths. A vertical growth of GeSn then occurs from the base layer to form a structural layer. The active zone is advantageously formed within the stack of the base and structural layers. The method makes it possible to obtain a lateral injection light source comprising a GeSn active zone exhibiting a reduced structural defect rate.