Buried Semiconductor Optical Device Parasitic Capacitance Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed semiconductor optical devices, such as electro-absorption modulators, face challenges in reducing parasitic capacitance to enhance their response at high speeds, particularly for applications requiring 25 Gbaud or 56 Gbaud operations in optical communication systems.
Innovation Solution
A buried type semiconductor optical device design featuring a semiconductor substrate with grooves and a convex portion forming a mesa stripe structure, a buried layer adjacent to the mesa stripe, and a passivation film arrangement that reduces parasitic capacitance by avoiding the formation of 'rabbit ears' and allowing for a narrower electrode width, thereby improving high-speed performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrode is disposed to cover the buried layer in a conventional buried type EA modulator, then the electrode can provide sufficient electrical connection, but the parasitic capacitance increases which deteriorates high-speed response
Solution Approach 1:
The electrode is divided into multiple segments: a first electrode portion on the mesa stripe structure, a second electrode portion on the buried layer, and a connection portion bridging them. This segmentation allows the electrode to maintain electrical connection while reducing the area of contact with the buried layer, thereby reducing parasitic capacitance and improving high-speed response.
Solution Approach 2:
The connection portion of the electrode is positioned to overlap with the grooves in plan view, creating a local region where the electrode avoids direct contact with the buried layer. This local modification reduces parasitic capacitance in the critical region while maintaining overall electrical connection functionality.
2Speed
If the electrode is narrowed to reduce parasitic capacitance, then high-speed response improves, but the electrical connection and heat dissipation may be compromised
Solution Approach 1:
The connection portion of the electrode extends in the depth direction (vertical dimension) to connect the first and second electrode portions. This vertical extension allows the electrode to maintain adequate electrical connection and heat dissipation capability while the planar width can be reduced to minimize parasitic capacitance with the buried layer.
Data Source
AI summary
A buried typed semiconductor optical device includes a semiconductor substrate having a pair of grooves extending in a first direction. An upper surface of a buried layer has a first region that is adjacent to a mesa stripe structure, overlaps with a corresponding one of the pair of grooves, is inclined so as to be higher in a second direction from the mesa stripe structure, and on which a passivation film is not formed. The upper surface of the buried layer has a second region that does not overlap with any of the pair of grooves, is flat, and is higher than a lower end of the first region, and on which the passivation film is formed. The upper surface of the buried layer has a connection region between the first region and the second region at a same height as the second region.