Light Receiving Element Constricted Portion Reduces Parasitic Capacitance
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Solution Overview
Problem
Light receiving elements for optical communication face a trade-off between mountability and high-speed responsiveness, as increasing mountability can lead to higher parasitic capacitance, which negatively impacts responsiveness.
Innovation Solution
Incorporating a constricted portion in the semiconductor layer of the light receiving element, specifically in the interface between conductive layers, reduces parasitic capacitance while maintaining mountability by exposing an edge on the internal surface of the constricted portion, allowing for a balance between the two.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the mesa diameter is increased to improve mountability, then the ease of mounting is improved, but the parasitic capacitance increases which deteriorates high-speed responsiveness
Solution Approach 1:
The patent applies local quality by creating a constricted portion at a specific location within the mesa structure - namely in the first conductive layer near the interface with the optical absorption layer. This localized constriction reduces the cross-sectional area at the critical junction region, thereby reducing parasitic capacitance without requiring a reduction in the overall mesa diameter, thus maintaining mountability while improving high-speed responsiveness
Solution Approach 2:
The patent introduces a dimensional variation within the mesa structure by creating a constricted portion that reduces the cross-sectional area at a specific height level. This vertical dimensioning approach allows the mesa to maintain a larger footprint for mountability while having a constricted region that reduces capacitance, effectively using dimensional variation to resolve the contradiction
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 effectively balances mountability and high-speed responsiveness by minimizing parasitic capacitance even with larger mesa diameters, enhancing the element's performance in optical communication devices.
Implementation Method 1
This allows an element to have a smaller capacitance compared to the case where the constricted portion is not provided in the mesa portion. In addition, even in the case of a larger mesa diameter, it is possible to suppress an increase in the parasitic capacitance of the element.
Data Source
AI summary
A light receiving element (1) according to an embodiment of the disclosure includes a semiconductor layer (20) in which a photodiode having a PIN structure is provided in a mesa portion having a pillar shape. The photodiode includes a first conductive layer (21), an optical absorption layer (23), and a second conductive layer (24) having a light incident surface. In the light receiving element (1), the semiconductor layer (20) includes, in the vicinity of an interface between the first conductive layer (21) and the optical absorption layer (23), a constricted portion (26) that is the most constricted of the first conductive layer (21). The interface has an end exposed on an internal surface of the constricted portion (26).