Npin Semiconductor Optical Modulator Hole Accumulation
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Solution Overview
Problem
Npin-type semiconductor optical modulators face challenges with high reverse voltage stability due to hole accumulation in the p-type cladding layer caused by light absorption, leading to increased electron current and frequency dispersion, and complex manufacturing processes required to address these issues.
Innovation Solution
The semiconductor optical modulator design includes a p-type cladding layer electrically connected to an electrode, forming a mesa structure with a p-type ohmic region on the side surface, and using a type II hetero junction with a semiconductor material having lower electron affinity to enhance barrier effectiveness, eliminating hole accumulation without requiring conductive type changes through Zn diffusion or Be ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a p-type cladding layer is used in npin-type optical modulator, then optical confinement is improved, but hole accumulation occurs causing frequency dispersion and reduced reliability
Solution Approach 1:
An n-type intermediate layer is introduced between the p-type cladding layer and the core layer. This intermediary layer prevents holes generated in the core layer from accumulating in the p-type cladding layer, thereby eliminating frequency dispersion while maintaining effective optical confinement. The intermediate layer acts as a barrier that blocks hole migration without compromising the optical guiding function.
2Reliability
If conventional methods (Zn diffusion or Be ion implantation) are used to change conductive type, then hole accumulation is prevented, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of using complex post-growth processes like Zn diffusion or Be ion implantation to change the conductive type of the intermediate layer, the invention utilizes parameter changes during the epitaxial growth process itself. By adjusting doping conditions and layer composition during growth, the intermediate layer is formed with the desired n-type conductivity directly, simplifying the manufacturing process while effectively preventing hole accumulation.
3Stability of the object's composition
If p-type cladding layer is used, then optical waveguide performance is improved, but phototransistor behavior increases electron current
Solution Approach 1:
The n-type intermediate layer serves as a mediator that blocks the flow of electrons from the n-type cladding layer to the p-type cladding layer. This prevents the phototransistor effect where accumulated holes would attract electrons across the junction, thereby reducing harmful electron current while preserving the optical waveguide performance provided by the p-type cladding layer.
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 design achieves higher reverse voltage stability and simplified manufacturing, reducing costs while preventing phototransistor behavior and maintaining low driving voltage, resulting in more stable and cost-effective optical modulators.
Implementation Method 1
The operation principle of the LN modulator is to couple an optical waveguide with an electrical waveguide, inducing a change in refractive index based on the electro-optic effect by an electrical signal input and creating a phase change in the optical signal.
Data Source
AI summary
The present invention can provide an npin-type optical modulator that has a high withstand voltage and is easily fabricated. A semiconductor optical amplifier (10) according to an embodiment of the present invention is an npin-type semiconductor optical modulator in which layers are sequentially stacked, with a cathode layer (12-1) arranged on the substrate side, including at least a first n-type cladding layer (13-1), a p-type cladding layer (14), a core layer (17) and a second n-type cladding layer (13-2). In this semiconductor optical modulator, the p-type cladding layer (14) is electrically connected to an electrode (18-1) of the cathode layer. Accordingly, the accumulation of holes in the p-type cladding layer associated with light absorption in the npin-type optical modulator can be absorbed in the electrode on the negative side. This npin-type semiconductor optical modulator can be comparatively easily fabricated using conventional semiconductor manufacturing techniques by adopting a mesa type waveguide structure.