Quantum Dot ToF Photodetectors for Silicon NIR Sensing
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Solution Overview
Problem
Current time-of-flight (TOF) sensors face challenges in efficiently operating in the near-infrared (NIR) spectrum due to limitations in silicon absorption and the high cost and bulkiness of infrared sensors, making it difficult to achieve low-cost, high-efficiency, small form factor, and low-power applications for dual wavelength operation in both visible and NIR spectrums.
Innovation Solution
A TOF sensor design incorporating a silicon-based photodetector array with quantum dot particles sensitive to the NIR region, which converts optical energy into electrical energy, coupled with a processing circuit to calculate the time-of-flight of NIR light, enabling efficient operation across both visible and NIR spectrums without the need for cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard silicon photodiodes are used for TOF sensors, then visible light detection is achieved, but NIR detection efficiency deteriorates due to sharply decreasing absorption around 900 nm
Solution Approach 1:
The patent changes the material parameters of the photosensitive layer by incorporating quantum dot particles with specific bandgap energies that absorb NIR light wavelengths (700-2500nm). This parameter change enables the silicon-based photodiode to detect NIR light while maintaining visible light detection capability, resolving the contradiction between visible light operation and NIR detection efficiency
Solution Approach 2:
The patent creates a composite photosensitive layer combining silicon-based material with quantum dot particles. This composite structure leverages the complementary absorption characteristics of silicon (visible light) and quantum dots (NIR light), enabling dual-wavelength detection and resolving the contradiction between visible and NIR detection efficiency
2Measurement precision
If dedicated infrared sensors (InGaAs) are used for NIR detection, then quantum efficiency in NIR region is improved, but cost and device complexity increase significantly
Solution Approach 1:
The patent makes the silicon-based photodiode universal by enabling it to detect both visible light and NIR light through the quantum dot enhancement. This multi-functionality eliminates the need for separate InGaAs infrared sensors, reducing device complexity and cost while maintaining high NIR quantum efficiency
Solution Approach 2:
The patent uses quantum dot particles that can be synthesized and integrated using CMOS-compatible processes, creating a simplified copy of infrared sensor functionality within the standard silicon photodiode structure, thereby avoiding the complexity of dedicated InGaAs sensor fabrication
3Measurement precision
If III-V materials are added to silicon processing for infrared detection, then NIR detection capability is improved, but manufacturing complexity and contamination risk increase
Solution Approach 1:
The patent replaces expensive and complex III-V material layers with quantum dot particles that can be deposited using simpler, CMOS-compatible techniques. The quantum dots serve as a disposable-like additive layer that provides NIR functionality without requiring complex heteroepitaxial growth processes, thereby improving ease of manufacture
Solution Approach 2:
The quantum dot particles act as an intermediary substance between the silicon substrate and the desired NIR detection functionality. They mediate the interaction between visible/NIR light and the silicon photodiode, enabling infrared detection without direct integration of complex III-V material structures
4Measurement precision
If traditional infrared sensors are used for NIR detection, then detection efficiency is improved, but device size and power consumption increase due to cooling requirements
Solution Approach 1:
The quantum dot-enhanced silicon photodiode is self-service in the sense that it operates at room temperature without requiring external cooling systems. The quantum dots' inherent optical properties enable NIR detection efficiency without the thermal management infrastructure needed by traditional infrared sensors, reducing device size and weight
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 solution allows for high-efficiency, low-cost, and compact TOF sensors capable of dual wavelength operation, improving image capture and depth mapping in various environmental conditions without the drawbacks of traditional infrared sensors.
Implementation Method 1
the plurality of quantum dot particles converts optical energy into electrical energy to generate an electrical current in response to receiving NIR light
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A time-of-flight (ToF) sensor includes a photodetector array and a processing circuit. The photodetector array includes a plurality of photodetectors wherein each photodetector of the photodetector array includes a silicon-based, light-sensitive diode. Each silicon-based, light-sensitive diode includes a photosensitive layer comprising a plurality of quantum dot particles sensitive to a near infrared (NIR) region of an electromagnetic spectrum, wherein the plurality of quantum dot particles converts optical energy into electrical energy to generate an electrical current in response to receiving NIR light having a wavelength in the NIR region. The processing circuit is configured to receive the electrical current and calculate a time-of-flight of the received NIR light based on the electrical current.