Curved Photodetector Structure for Lower Dark Current
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Solution Overview
Problem
Photonic integrated circuits (PICs) face challenges with dark current due to defects and dislocations at the interface between semiconductor materials like silicon and germanium, which affects device performance and noise levels.
Innovation Solution
A semiconductor device design with a photodetector having an arcing lower surface that reduces the contact area with the substrate, minimizing defects and dislocations, and utilizing a waveguide structure to guide photons into the photodetector, which is configured to absorb electromagnetic radiation in telecom optical wavelength bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the photodetector uses a planar interface with the semiconductor substrate, then the contact area is large which provides good electrical connection, but the defects and dislocations at the interface increase causing high dark current
Solution Approach 1:
The photodetector employs a curved lower surface instead of a planar interface with the semiconductor substrate. This curvature reduces the contact area between the photodetector and substrate, thereby minimizing the region where defects and dislocations can form at the heterostructure interface. The reduced contact area directly lowers the dark current while maintaining sufficient electrical connection through optimized contact geometry.
2Reliability
If the photodetector contact area with substrate is reduced to minimize defects, then dark current decreases, but electrical connection quality may deteriorate
Solution Approach 1:
The invention applies local quality by creating a non-uniform contact interface where the curved surface provides different contact characteristics at different locations. The curvature concentrates the contact area in specific regions that maintain good electrical connection while avoiding areas prone to defect formation. This localized optimization allows dark current reduction without compromising overall electrical connection quality.
3Reliability
If the photodetector interface area is minimized to reduce defects, then dark current and noise are reduced, but optical absorption efficiency may be affected
Solution Approach 1:
The invention compensates for the reduced contact area by optimizing the vertical dimension and lateral geometry of the photodetector structure. The curved surface is designed with specific radius and profile to maintain adequate optical mode overlap and absorption efficiency. By transitioning from a two-dimensional planar contact to a three-dimensional curved interface, the design preserves optical absorption while minimizing defect-prone contact areas.
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 design reduces dark current and improves device performance by minimizing defects and dislocations, leading to lower noise levels and enhanced absorption capabilities in the telecom optical wavelength range.
Implementation Method 1
The waveguide structure is configured to guide one or more photons from a first location into the photodetector
Implementation Method 2
The photodetector is configured to absorb the one or more photons and generate electrical signals corresponding to the one or more photons
Data Source
AI summary
Various embodiments of the present disclosure are directed towards a semiconductor device. The semiconductor device includes a first doped region having a first doping type disposed in a semiconductor substrate. A second doped region having a second doping type different than the first doping type is disposed in the semiconductor substrate and laterally spaced from the first doped region. A waveguide structure is disposed in the semiconductor substrate and laterally between the first doped region and the second doped region. A photodetector is disposed at least partially in the semiconductor substrate and laterally between the first doped region and the second doped region. The waveguide structure is configured to guide one or more photons into the photodetector. The photodetector has an upper surface that continuously arcs between opposite sidewalls of the photodetector. The photodetector has a lower surface that continuously arcs between the opposite sidewalls of the photodetector.