Silicon Schottky Photodetector Field Plate Responsivity
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Solution Overview
Problem
Conventional silicon-based Schottky barrier infrared photodetectors have low responsivity and high dark current due to normal incidence design, requiring large detection areas and cooling, and are limited by the non-planar geometry of rib waveguide structures, which are difficult to manufacture and less efficient.
Innovation Solution
A planar, waveguide-based silicon-based Schottky barrier infrared photodetector with an additional field plate is introduced, where the field plate creates an electric field to adjust the direction and momentum of 'hot' carriers over the Schottky barrier, increasing photocurrent and responsivity, and is fabricated using standard CMOS processing steps without altering existing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If normal incidence photodetector design is used, then simple structure is achieved, but optical absorption efficiency is extremely low
Solution Approach 1:
The patent transitions from normal incidence (perpendicular) light detection to lateral incidence detection by integrating the photodetector with a rib waveguide structure. The light propagates laterally along the waveguide and interacts with the active detection area from the side, fundamentally changing the dimension of light interaction and enabling efficient absorption without requiring complex optical components.
Solution Approach 2:
The rib waveguide acts as an intermediary structure that guides light laterally to the active detection area. Instead of light directly incident on the detector from above, the waveguide mediates the light delivery, allowing the optical signal to travel along the waveguide and be absorbed by the detector positioned at the waveguide output.
2Use of energy by moving object
If detection area is increased to collect sufficient optical energy, then optical energy collection is improved, but dark current increases
Solution Approach 1:
By using lateral incidence detection through the rib waveguide structure, the patent achieves efficient optical energy collection with a compact active detection area. The lateral geometry allows the light to interact with the detector along the waveguide length, providing sufficient optical energy collection without requiring a large detector area that would increase dark current.
3Loss of energy
If rib waveguide structure is implemented to improve absorption efficiency, then optical absorption is enhanced, but manufacturing difficulty increases significantly
Solution Approach 1:
The patent combines the rib waveguide structure and the Schottky barrier photodetector into a single integrated device using standard CMOS processing. The waveguide and detector are formed in the same fabrication process, merging two previously separate components into one monolithic structure that maintains high absorption efficiency while enabling scalable manufacturing.
Solution Approach 2:
The patent optimizes the waveguide dimensions (width, height, and length) and detector parameters (active area size, Schottky barrier thickness) to achieve efficient light absorption while maintaining compatibility with standard CMOS fabrication processes. By carefully controlling these parameters, the design balances optical performance with manufacturability.
4Ease of manufacture
If conventional processing technologies are used, then manufacturing simplicity is maintained, but control of waveguide dimensions and smoothness is poor
Solution Approach 1:
The patent employs standard CMOS processing techniques with optimized process parameters to achieve precise control of waveguide dimensions. By adjusting fabrication parameters such as etch depth, deposition thickness, and annealing conditions, the patent achieves sub-micron dimension control and smooth waveguide surfaces using conventional manufacturing equipment.
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 solution enhances responsivity by aligning 'hot' carriers with the Schottky barrier, allowing for higher photocurrent generation and reduced dark current, while maintaining compatibility with CMOS processing and operating at room temperature.
Implementation Method 1
the field plate creates an electric field to adjust the direction and momentum of 'hot' carriers over the Schottky barrier
Implementation Method 2
Semiconductor devices using metal-semiconductor barriers (referred to as Schottky barriers) instead of p-n junctions have been developed to convert incident light into electrical energy
Implementation Method 3
a planar, waveguide-based IR optical detector
Data Source
Figure 1~3
Figure 4~5
AI summary
A planar, waveguide-based silicon Schottky barrier photodetector includes a third terminal in the form of a field plate to improve the responsivity of the detector. Preferably, a suicide used for the detection region is formed during a processing step where other suicide contact regions are being formed. The field plate is preferably formed as part of the first or second layer of CMOS metallization and is controlled by an applied voltage to modify the electric field in the vicinity of the detector's suicide layer. By modifying the electric field, the responsivity of the device is "tuned" so as to adjust the momentum of "hot" carriers (electrons or holes, depending on the conductivity of the silicon) with respect to the Schottky barrier of the device. The applied potential functions to align with the direction of momentum of the "hot" carriers in the preferred direction "normal" to the silicon-silicide interface, allowing for an increased number to move over the Schottky barrier and add to the generated photocurrent.