Infrared Detector SNR via AlGaInSb Layer Optimization
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Solution Overview
Problem
Infrared detecting devices with small semiconductor bandgaps face challenges in achieving sufficient PN diode characteristics due to high intrinsic carrier density, leading to increased leakage current and reduced signal-to-noise ratio (SNR) at room temperature.
Innovation Solution
The design incorporates a semiconductor substrate with multiple compound semiconductor layers, including a light receiving layer with In and Sb, and a second compound semiconductor layer with Al and Sb, optimized in terms of composition and thickness to suppress diffusion current and enhance device resistance, thereby improving SNR characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a semiconductor with a small bandgap (≤0.62 eV) is used to detect infrared rays with wavelength ≥2 μm, then the infrared detection capability is improved, but the intrinsic carrier density increases due to thermally excited carriers, causing increased leakage current and reduced device resistance
Solution Approach 1:
The patent changes the material composition parameters by introducing Al composition (nAl) and Ga composition (nGa) in the compound semiconductor layers, and optimizes the thickness parameters (m1B, m2) to achieve the desired balance between infrared detection capability and leakage current suppression at room temperature
Solution Approach 2:
The patent uses compound semiconductor materials with specific compositions (Alx-yGayIn1-xSb and InySb1-y) instead of simple semiconductors, creating a composite structure that maintains small bandgap for infrared detection while suppressing thermal carrier generation through optimized material composition
2Difficulty of detecting and measuring
If the intrinsic carrier density is high in a semiconductor with small bandgap, then the infrared absorption is improved, but the leakage current (diffusion current and dark current) increases
Solution Approach 1:
The patent applies different material compositions and structures at different locations: the light receiving layer has specific Al and Ga compositions optimized for infrared absorption, while the first and second compound semiconductor layers have different compositions and thicknesses designed to suppress diffusion current, creating local optimization of both absorption and leakage suppression
Solution Approach 2:
The patent introduces a layered structure with multiple dimensions (first compound semiconductor layer, light receiving layer, second compound semiconductor layer) rather than using a single uniform layer, allowing independent optimization of infrared absorption and leakage current suppression in different layers
3Reliability
If a cooling mechanism is added to suppress thermally excited carriers, then the leakage current is reduced and device resistance increases, but the device complexity and size increase
Solution Approach 1:
The patent extracts and eliminates the need for cooling mechanisms by using room-temperature operable compound semiconductor materials with optimized compositions that inherently suppress thermal carrier generation, thereby removing the complex cooling system while maintaining high device resistance
Solution Approach 2:
The patent replaces expensive and complex cooling mechanisms with simple, room-temperature-operating compound semiconductor structures that achieve the same effect of suppressing thermal carriers through material composition optimization rather than active cooling
4Reliability
If the Al composition difference between the second compound semiconductor layer and light receiving layer is increased to suppress diffusion current, then the device resistance increases, but the product of thickness and composition difference should not be too large
Solution Approach 1:
The patent optimizes the Al composition parameter (nAl) and thickness parameter (m2) of the second compound semiconductor layer to achieve the optimal balance, ensuring that the product |n2-nlight|×m2 is within the appropriate range to suppress diffusion current while maintaining reasonable device structure
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 configuration effectively increases device resistance and reduces line defect density, resulting in improved SNR characteristics for infrared detecting devices, enabling better performance at room temperature.
Implementation Method 1
electrons and holes generated by the absorbed infrared rays in the light receiving layer are converted into electric signals through charge separation by the internal electric field in a depletion layer at the PN junction
Implementation Method 2
a specific gas absorbs infrared rays having a specific wavelength
Implementation Method 3
the first compound semiconductor layer comprises, in the stated order: a first A layer, a first B layer, and a first C layer... |n2−nlight|×m2≤|n1B−n1A|×m1B
Data Source
AI summary
Provided is an infrared detecting device with high SNR. The infrared detecting device includes: a semiconductor substrate; a first compound semiconductor layer; a light receiving layer formed on the first compound semiconductor layer and containing at least In and Sb and having a predetermined range(s) of Al or Al and Ga proportion(s); a third compound semiconductor layer; and a second compound semiconductor layer containing at least In, Al, and Sb and having a predetermined range(s) of Al or Al and Ga proportion(s), in which the first compound semiconductor layer includes, in the stated order, a first A layer, a first B layer, and a first C layer, each containing at least In and Sb and having a predetermined range(s) of Al or Al and Ga proportion(s), and the proportion(s) of the Al composition or the Al composition and the Ga composition of each layer satisfy a predetermined relation(s).