Upconversion Layered Silicon Sensor for SWIR Detection
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Solution Overview
Problem
Silicon-based image sensors are limited to detecting wavelengths up to 1100 nm, and extending their sensitivity to longer infrared wavelengths, such as SWIR, MWIR, and LWIR, requires expensive materials and techniques, making them costly.
Innovation Solution
Incorporating an upconversion layer with crystals that convert electromagnetic radiation above 1100 nm to wavelengths detectable by a silicon substrate, enhancing quantum efficiency through scattering and stabilizing the silicon substrate's back surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If expensive materials and techniques are used to detect infrared wavelengths greater than 1100 nm, then the sensor can detect SWIR, MWIR, and LWIR wavelengths, but the sensor cost increases significantly
Solution Approach 1:
The patent introduces an upconversion layer as an intermediary component between the incident infrared radiation and the silicon substrate. This layer contains phosphors that absorb infrared wavelengths greater than 1100 nm and convert them to visible wavelengths that the silicon substrate can detect. This mediator enables the use of inexpensive silicon-based sensors while achieving infrared detection capability, thereby resolving the contradiction between extended wavelength range and low cost.
2Productivity
If the photo-sensitive silicon substrate is made thicker to increase quantum efficiency, then more light can be detected, but the device size and manufacturing complexity increase
Solution Approach 1:
The patent changes the wavelength parameter of the incident radiation through the upconversion process. By converting infrared wavelengths to visible wavelengths, the radiation matches the absorption characteristics of the silicon substrate more effectively. This parameter transformation allows the use of thinner substrates while maintaining or improving quantum efficiency, thus resolving the contradiction between detection efficiency and device complexity.
3Ease of manufacture
If the sensor is designed to detect only wavelengths up to 1100 nm, then the sensor cost remains low, but the sensor cannot detect SWIR, MWIR, and LWIR wavelengths
Solution Approach 1:
The patent makes the silicon substrate multi-functional by enabling it to detect both visible wavelengths (through direct detection) and infrared wavelengths (through upconversion). The upconversion layer allows the same substrate to handle multiple wavelength ranges, effectively creating a universal sensor that maintains low cost while achieving extended spectral coverage.
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
Enables silicon-based sensors to detect a broader wavelength range, including SWIR, MWIR, and LWIR, at a lower cost by using a cost-effective upconversion layer that maintains sensor performance without increasing size, weight, or power.
Implementation Method 1
an upconversion layer configured to convert electromagnetic radiation having a first wavelength greater than 1100 nanometers (nm) to electromagnetic radiation having a second wavelength less than or equal to 1100 nm
Implementation Method 2
the upconversion layer includes crystals having a dopant selected to absorb the incident electromagnetic radiation at a first range of wavelengths (e.g., greater than or equal to 1100 nm) and to emit electromagnetic radiation at a second range of wavelengths (e.g., less than 1100 nm)
Implementation Method 3
the upconversion layer may provide scattering configured to increase the angle of incidence of electromagnetic radiation at the second range of wavelengths to increase the quantum efficiency of the sensor, e.g., via a longer mean path length within the photo-sensitive material (silicon)
Implementation Method 4
the upconversion layer may provide a negative electric charge configured to stabilize the back surface of a photo-sensitive silicon substrate of a back side illuminated (BSI) sensor
Data Source
AI summary
In general, the disclosure describes a sensor comprising a photo-sensitive silicon substrate configured to detect ultraviolet (UV), visible, and near-infrared (NIR) light and an upconversion layer comprising a plurality of crystals configured to convert short wave infrared light to UV, visible, or NIR light. An example sensor includes an upconversion layer comprising a plurality of crystals configured to convert electromagnetic radiation comprising a first range of wavelengths greater than 1100 nm to electromagnetic radiation comprising a second range of wavelengths less than or equal to 1100 nm and a photo-sensitive silicon substrate configured to detect the electromagnetic radiation comprising the second range of wavelengths.