Optical Waveguide Photodiode Contact Area Reduction
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Solution Overview
Problem
Optical waveguide type photodiodes with field confinement structures experience losses due to peripheral regions without electric fields, leading to reduced sensitivity and reliability, as only photocarriers generated under the contact layer contribute effectively to operation, while others behave as losses.
Innovation Solution
An optical waveguide integrated light receiving element with a second contact layer of smaller area than the light absorption layer, arranged inside it, and optically coupled with the waveguide, which confines the electric field and enhances effective operation area, thereby minimizing losses and improving sensitivity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a field confinement structure is implemented in optical waveguide type photodiodes, then reliability is improved by confining electric field inside the element, but loss increases due to peripheral regions without electric fields causing photocarriers to behave as losses
Solution Approach 1:
The patent extends the electric field confinement from a two-dimensional planar structure to a three-dimensional configuration by slanting the separation interface between the photodiode and waveguide. This angular extension allows the electric field to be confined more effectively throughout the volume of the light absorption layer, preventing photocarrier loss in peripheral regions while maintaining reliability.
2Measurement precision
If the light absorption layer is made thicker to increase light responsivity, then light absorption efficiency is improved, but operation speed decreases due to longer carrier travel distance
Solution Approach 1:
The patent introduces a dynamic field distribution through the slanted separation interface, creating a non-uniform electric field that is stronger near the waveguide interface and gradually weaker toward the bulk. This dynamic field configuration accelerates carrier collection in the thick absorption layer without requiring the entire layer to have high field strength, thus maintaining both high responsivity and fast operation speed.
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 configuration effectively suppresses losses and enhances the sensitivity and reliability of optical waveguide type photodiodes by ensuring that all photocarriers generated within the effective operation area contribute to the photonic conversion process.
Implementation Method 1
an optical waveguide type light receiving element in which an optical waveguide and a light receiving element are integrated
Implementation Method 2
a light receiving element such as a photodiode (PD) or an avalanche photodiode (APD) configured to convert incident light into a current
Implementation Method 3
the APD has a function of accelerating, under a high electric field, photoelectrons generated in the element and thus colliding them against a lattice to ionize, thereby amplifying the carrier
Data Source
Figure 1A~1C
Figure 2~3
Figure 4~5
AI summary
An optical waveguide integrated light receiving element includes an optical waveguide (105) arranged on a side of a second contact layer (102) opposite to a side where a light absorption layer (103) is arranged, having a waveguide direction parallel to a plane of the light absorption layer (103), and optically coupled with the second contact layer (102). The second contact layer (102) has, in a planar view, a size of an area smaller than that of the light absorption layer (103) and arranged inside the light absorption layer (103).