Arced Ge Photodetector Interface for Low-Dark-Current PICs
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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, particularly between silicon (Si) and germanium (Ge), which affects the performance of silicon photonic devices used in fiber optic communication systems.
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 silicon substrate, then the manufacturing process is simple, but defects and dislocations occur at the interface causing high dark current
Solution Approach 1:
The patent applies curvature by forming an arced lower surface on the germanium photodetector that contacts the silicon substrate. This curved interface reduces the contact area between the two semiconductor materials, thereby minimizing lattice mismatch defects and dislocations that cause dark current. The arced surface is formed through selective etching processes that create a non-planar geometry at the Ge-Si interface.
2Reliability
If the photodetector contact area with substrate is reduced, then defects and dislocations are minimized, but the absorption of photons may be reduced
Solution Approach 1:
The patent segments the photodetector structure into distinct functional regions: an arced lower surface for minimal substrate contact to reduce defects, a bulk germanium region for photon absorption, and an upper surface for electrical contact. This segmentation allows the defect-prone interface area to be minimized while maintaining sufficient absorption volume in the bulk material.
Solution Approach 2:
The patent transitions from a two-dimensional planar interface to a three-dimensional arced surface configuration. This dimensional change allows the interface to curve away from the substrate, reducing contact area in the horizontal plane while maintaining vertical absorption path length for incident photons.
3Strength
If the photodetector has a larger contact area with substrate, then the mechanical support is stronger, but more defects and dislocations are generated
Solution Approach 1:
The arced lower surface concentrates mechanical support at specific points of contact with the substrate rather than distributing it across a large planar area. The curved geometry provides sufficient mechanical anchoring while minimizing the interface area where lattice mismatch defects occur between germanium and silicon.
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 at the interface, leading to reduced noise and enhanced absorption capabilities for silicon photonic devices.
Implementation Method 1
a waveguide structure 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 disposed in a semiconductor substrate and a second doped region disposed in the semiconductor substrate. A photodetector is disposed between the first doped region and the second doped region. The photodetector has a lower surface that arcs between opposing sidewalls of the photodetector in a cross-sectional view. The first doped region and the second doped region contact the lower surface of the photodetector.