Semiconductor Optical Modulator With Segmented Junctions
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Solution Overview
Problem
The existing semiconductor optical modulators with a single p-n junction in a cladding layer have low modulation efficiency due to a smaller variation of the electric field in the core layer when a modulated electrical signal is applied, leading to reduced voltage applied to the core layer and decreased electric field, which in turn reduces optical modulation efficiency.
Innovation Solution
A semiconductor optical modulator with a stacked layer structure including multiple p-n junctions and p-i junctions, where the i-type semiconductor region is depleted when a voltage is applied, forming a barrier for drift current and reducing optical absorption, with specific dopant concentrations and thicknesses for the p-type semiconductor regions to enhance depletion and reduce optical loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single p-n junction is disposed in a cladding layer, then the energy band profile is easily controlled and stable operation is achieved, but the electric field variation in the core layer is small leading to low modulation efficiency
Solution Approach 1:
The single p-n junction is segmented into multiple p-n junctions (first p-n junction in the first cladding layer, second p-n junction in the second cladding layer) with an i-type region in between. This segmentation allows each junction to contribute to electric field formation independently, creating larger electric field variation in the core layer for improved modulation efficiency while maintaining stable operation through the nin-type heterostructure configuration.
Solution Approach 2:
An i-type semiconductor region is introduced as an intermediary between the two p-n junctions. This i-type region acts as a mediator that enhances the electric field variation in the core layer when voltage is applied, while the overall nin-type heterostructure maintains the stable energy band profile. The i-type region allows for better electric field control without compromising the stability provided by the heterostructure.
2Device complexity
If a p-n junction is disposed in a cladding layer, then the structure is simplified, but part of the applied voltage is consumed by the depleted p-n junction reducing the voltage applied to the core layer
Solution Approach 1:
The voltage application is segmented across multiple junctions rather than a single junction. The first p-n junction is reverse-biased to create a depletion region, while the second p-n junction is forward-biased or less reverse-biased, allowing the applied voltage to be distributed in a way that maximizes the electric field in the core layer. This segmentation improves voltage utilization efficiency while maintaining structural simplicity through the stacked layer configuration.
Solution Approach 2:
Different bias conditions are applied to different p-n junctions to create local quality differences. The first p-n junction region has high electric field due to reverse bias for carrier depletion, while the second p-n junction region has different bias characteristics. This local differentiation optimizes voltage utilization in the core layer while keeping the overall structure relatively simple.
3Ease of manufacture
If the core layer contains p-type semiconductor regions, then the structure is easier to manufacture, but optical absorption increases due to carriers in the p-type regions
Solution Approach 1:
The harmful effect of carrier-induced optical absorption in p-type regions is extracted or removed by applying reverse bias to the first p-n junction. This creates a depletion region that extracts carriers from the p-type semiconductor regions in the core layer, reducing optical absorption loss while maintaining the ease of manufacturing associated with p-type doped regions.
Solution Approach 2:
The carrier concentration in the p-type semiconductor regions is made dynamic rather than static. By applying reverse bias to the first p-n junction, the depletion region dynamically adjusts carrier concentration in the adjacent p-type regions during operation. This dynamic control reduces optical absorption when needed while maintaining the structural simplicity and manufacturing ease of p-type doped layers.
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 modulator achieves improved modulation efficiency by increasing the electric field in the core layer and reducing optical absorption loss, allowing for more effective optical modulation with reduced power consumption.
Implementation Method 1
when a voltage is applied between the first n-type semiconductor region and the second n-type semiconductor region, the i-type semiconductor region in the core layer is depleted of carriers
Implementation Method 2
a region from the first p-n junction to the second p-n junction acts as a barrier for drift current
Implementation Method 3
when a modulated electrical signal (voltage signal) is applied to the optical modulator... the electric field in the core layer
Data Source
AI summary
A semiconductor optical modulator includes a first n-type semiconductor region, a first p-type semiconductor region, an i-type semiconductor region, a second p-type semiconductor region, and a second n-type semiconductor region that constitute a stacked layer structure. The stacked layer structure includes a first cladding layer, a second cladding layer, and a core layer disposed between the first and second cladding layer. The first n-type semiconductor region and the first p-type semiconductor region form a first p-n junction disposed in an intermediate region between the first and second cladding layer. The second p-type semiconductor region and the second n-type semiconductor region form a second p-n junction disposed in the intermediate region or the second cladding layer. The intermediate region, the first n-type semiconductor region, and the second n-type semiconductor region include the core layer, the first cladding layer, and part or all of the second cladding layer, respectively.