SiN Waveguide Lateral Photodiode for 200 GHz Bandwidth
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Solution Overview
Problem
Existing photodetectors face challenges in achieving high opto-electrical bandwidth due to difficulties in integrating a SiN waveguide with a lateral photodiode, particularly due to thermal budget constraints and parasitic capacitance issues, which limit the opto-electrical -3 dB bandwidth to below 200 GHz.
Innovation Solution
The photodetector design includes a lateral photodiode with in-situ p-doped and n-doped contact regions, where the SiN waveguide is deposited before the contact regions, allowing direct contact and reducing thermal budget constraints, thereby achieving opto-electrical -3 dB bandwidths of 200 GHz or more by preventing parasitic capacitance and enhancing coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SiN waveguide is deposited after the contact regions, then the thermal budget constraints are satisfied, but parasitic capacitance increases and opto-electrical bandwidth decreases below 200 GHz
Solution Approach 1:
The SiN waveguide is deposited before the contact regions are formed, reversing the conventional sequence. This preliminary action allows the waveguide to be in direct contact with the light-sensitive region without introducing parasitic capacitance from subsequent doping processes, enabling opto-electrical bandwidths of 200 GHz or more.
2Reliability
If the SiN waveguide is deposited before the contact regions, then parasitic capacitance is reduced and opto-electrical bandwidth increases to 200 GHz or more, but the fabrication process complexity increases
Solution Approach 1:
By depositing the SiN waveguide layer early in the fabrication process using standard CMOS-compatible techniques, the design leverages existing process capabilities. The subsequent formation of contact regions through standard doping and metallization steps integrates seamlessly, avoiding the need for specialized equipment or processes.
3Reliability
If the light-sensitive region width is reduced to enhance coupling efficiency, then bandwidth improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the lateral width of the light-sensitive region to specific ranges (e.g., 200-500 nm) to achieve optimal coupling efficiency and bandwidth performance. This parameter optimization balances the need for high performance with the capabilities of standard fabrication processes, ensuring manufacturability while achieving 200 GHz or more bandwidth.
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 enables improved opto-electrical bandwidth and reduced RC time constant, allowing for faster receivers with enhanced coupling efficiency between the SiN waveguide and the light-sensitive region, overcoming previous limitations in photodetector performance.
Implementation Method 1
The SiN waveguide is arranged on top of the lateral photodiode along a vertical stacking direction that is perpendicular to the lateral stacking direction. The SiN waveguide is configured to guide electromagnetic radiation along a propagation direction.
Implementation Method 2
germanium (Ge) as a detector material due to its significantly better absorbance compared to silicon (Si) in the wavelength range used for optical communication
Implementation Method 3
germanium (Ge) as a detector material due to its significantly better absorbance compared to silicon (Si) in the wavelength range used for optical communication
Data Source
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AI summary
The invention relates to a photodetector for detecting electromagnetic radiation. The photodetector comprises a lateral photodiode and a SiN waveguide. The lateral photodiode comprises an in-situ p-doped contact region (112), an in-situ n-doped contact region (114) and, sandwiched between the p-doped contact region and n-doped contact region along a lateral stacking direction (109), an intrinsically doped light-sensitive region (108). The SiN waveguide (102) comprises SiN and is configured to guide electromagnetic radiation along a propagation direction (104), the SiN waveguide being arranged on top of the lateral photodiode along a vertical stacking direction (107) that is perpendicular to the lateral stacking direction (109). At least a part of the light-sensitive region and at least a part of the SiN waveguide form a common upper interface (116) at which the light-sensitive region is in direct contact with the SiN waveguide. Moreover, the light-sensitive region (108) has a lateral width (110) along the lateral stacking direction of 300 nm or less.