Broadband InGaAs Photodiode With Thin Window Layer for NIR Sensing
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Solution Overview
Problem
Existing non-invasive sensors require multiple detectors to cover a broad range of optical wavelengths, leading to increased size, complexity, and inaccuracies due to variations in optical radiation path lengths, which can be mitigated by using a single photodiode with an optimized window layer that enhances transmittance across visible and near-infrared wavelengths.
Innovation Solution
A photodiode with a thin InAlAs window layer, such as an enhanced InGaAs photodiode, is used to detect optical radiation across a broad range of wavelengths, replacing the need for multiple detectors and allowing for a more compact and accurate sensor design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple detectors are used to cover a broad range of optical wavelengths, then the detection capability across wavelengths is improved, but the device size and complexity increase
Solution Approach 1:
The patent applies universality by designing a single photodiode that performs multiple detection functions across different wavelength ranges. The photodiode structure with optimized anti-reflective coating and layer configuration enables it to detect both visible and near-infrared wavelengths effectively, replacing what would traditionally require multiple separate detectors. This multi-functional design reduces device complexity while maintaining broad detection capability.
Solution Approach 2:
The patent merges the functionality of multiple detectors into a single integrated photodiode structure. By combining different semiconductor layers (such as InGaAs and InP layers) with appropriate anti-reflective coatings, the device integrates the detection capabilities of what would otherwise be separate components, thereby reducing overall device size and simplifying the optical path while maintaining sensitivity across a broad spectral range.
2Adaptability or versatility
If multiple detectors are used to cover a broad range of optical wavelengths, then the detection capability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent merges multiple detector functions into a single photodiode structure that can be manufactured as one integrated component. The layered semiconductor structure with anti-reflective coatings is designed to be fabricated using standard semiconductor processing techniques, allowing a single manufacturing process to produce a device that performs multiple wavelength detections, thereby reducing assembly complexity and improving ease of manufacture compared to assembling multiple separate detectors.
Solution Approach 2:
The patent employs composite materials in the form of layered semiconductor structures (e.g., InGaAs absorption layer combined with InP window layer) and multi-layer anti-reflective coatings. These composite structures are designed to work together to achieve broad spectral response, and they can be fabricated using established semiconductor epitaxial growth techniques, making the manufacturing process feasible while maintaining enhanced detection capabilities.
3Strength
If a thin window layer is used to increase transmittance, then the signal strength is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the window layer and anti-reflective coating layers to achieve the desired balance between transmittance and manufacturing feasibility. By carefully selecting specific thickness parameters (such as quarter-wave thickness for anti-reflective coatings), the design maximizes optical transmittance while keeping the manufacturing precision requirements within achievable limits using standard semiconductor fabrication processes.
Solution Approach 2:
The patent applies local quality by creating spatially varying layer structures where different regions have different optical properties. The anti-reflective coating is designed with specific thickness variations across different wavelengths, and the semiconductor layers are structured to have optimized properties at different depths. This local optimization allows the thin window layer to provide high transmittance where needed while maintaining manufacturability through standardized layer deposition 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
This approach enables a non-invasive sensor to detect optical radiation with higher signal strength and reduced size, providing more accurate measurements of physiological parameters by utilizing a single detector that covers the range traditionally detected by multiple photodiodes.
Implementation Method 1
the thickness of the window layer can be minimized or the bandgap of the window layer can be maximized, or both, to increase the transmittance of the window layer for certain wavelengths of optical radiation
Implementation Method 2
a photodiode is disclosed herein that can detect optical radiation at a broad range of wavelengths and generate a detector signal responsive to the detected optical radiation
Data Source
AI summary
Embodiments of the present disclosure include a photodiode that can detect optical radiation at a broad range of wavelengths. The photodiode can be used as a detector of a non-invasive sensor, which can be used for measuring physiological parameters of a monitored patient. The photodiode can be part of an integrated semiconductor structure that generates a detector signal responsive to optical radiation at both visible and infrared wavelengths incident on the photodiode. The photodiode can include a layer that forms part of an external surface of the photodiode, which is disposed to receive the optical radiation incident on the photodiode and pass the optical radiation to one or more other layers of the photodiode.