Infrared Sensor Element With Narrow-Bandgap Layer for Low-Noise Imaging
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Solution Overview
Problem
Near-infrared (NIR) sensors face challenges due to strong ambient irradiation from sunlight and artificial lighting, which creates an undesirably large background signal, and NIR irradiation is attenuated by display materials, making imaging difficult and potentially harmful to the human ocular system.
Innovation Solution
A sensor element comprising a first epitaxial layer of p-doped silicon with an n-doped silicon zone and a second epitaxial layer of a semiconductor with a narrower bandgap, such as germanium or indium-gallium arsenide, which absorbs longer wavelengths and generates minority charge carriers for improved photocurrent collection, integrated into imaging sensor arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NIR sensors operate at 850 nanometers to detect infrared radiation, then detection capability is achieved, but background noise from sunlight and artificial lighting increases
Solution Approach 1:
The patent changes the operating wavelength parameter from 850 nm to longer infrared wavelengths (1000-3000 nm) where sunlight and artificial lighting have minimal emission. This parameter shift moves the sensor operation to an atmospheric transmission window where ambient background radiation is significantly reduced, thereby improving signal-to-noise ratio while maintaining detection capability
Solution Approach 2:
The patent introduces a specialized photodetector material as an intermediary component that is specifically sensitive to longer infrared wavelengths (1000-3000 nm) rather than conventional NIR wavelengths. This intermediary detector selectively responds to the desired wavelength range while being inherently insensitive to the dominant 850 nm ambient radiation, effectively filtering out background noise at the detector level
2Ease of manufacture
If silicon-based sensors are used for NIR detection, then manufacturing compatibility is maintained, but sensitivity at longer infrared wavelengths decreases
Solution Approach 1:
The patent employs composite material structures that combine silicon-based components with specialized photodetector materials having narrower bandgaps suitable for longer infrared wavelengths. The composite structure leverages the manufacturing advantages of silicon technology while incorporating materials like InGaAs or HgCdTe that provide enhanced sensitivity at 1000-3000 nm wavelengths, thus achieving both ease of manufacture and improved sensitivity
Solution Approach 2:
The sensor structure is segmented into distinct functional layers: a silicon-based substrate providing mechanical support and standard CMOS compatibility, and a separate photodetector layer made from specialized materials optimized for longer infrared wavelengths. This segmentation allows each layer to be optimized for its specific function while maintaining overall manufacturing feasibility through established semiconductor fabrication processes
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
Enhances sensitivity over infrared bands, reduces background noise, and improves imaging performance by collecting photocurrent effectively while minimizing dark current, enabling more efficient and safer imaging.
Implementation Method 1
The second epitaxial layer is arranged on the epitaxy side of the first epitaxial layer and comprises a semiconductor having a narrower bandgap than silicon
Data Source
AI summary
One aspect of this disclosure relates to a sensor element comprising first and second epitaxial layers and one or more electrode structures. The first epitaxial layer includes a base of p-doped silicon and a zone of n-doped silicon arranged within the base, the zone being aligned to an epitaxy side of the first epitaxial layer. The second epitaxial layer is arranged on the epitaxy side of the first epitaxial layer and comprises a semiconductor having a narrower bandgap than silicon. The one or more electrode structures are arranged on the epitaxy side of the first epitaxial layer, adjacent the second epitaxial layer.