Superlattice Infrared Detector Structure for Low-Dark-Current e-SWIR
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Solution Overview
Problem
Current infrared detector systems face limitations in detecting longer wavelengths due to their inherent bandgap properties, leading to higher dark current and reduced sensitivity, especially in extended short-wave infrared (e-SWIR) ranges.
Innovation Solution
The implementation of a superlattice-based detector structure with alternating layers of semiconductor materials, such as InGaAs and GaAsSb, which forms a p-n junction and graded bandgap, allowing for extended cut-off wavelengths and reduced dark current by facilitating the flow of photogenerated carriers and mitigating generation-recombination current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional infrared detector structures are used, then detection capability at standard wavelengths is maintained, but detection capability at extended longer wavelengths deteriorates due to higher dark current
Solution Approach 1:
The patent applies parameter changes by systematically varying the bandgap structure through multiple superlattice layers with different material compositions (InGaAs, GaAsSb, InAlAs) and thicknesses. This creates a graded bandgap profile that extends the cut-off wavelength from 1.7μm to beyond 3μm while controlling dark current through optimized layer parameters
Solution Approach 2:
The patent employs composite materials by combining multiple semiconductor materials with different bandgap properties in a superlattice structure. The alternating layers of InGaAs (narrower bandgap), GaAsSb (wider bandgap), and InAlAs create a composite structure that achieves extended wavelength detection while maintaining low dark current through the synergistic properties of constituent materials
2Measurement precision
If the bandgap is reduced to detect longer wavelengths, then extended short-wave infrared detection is enabled, but dark current increases
Solution Approach 1:
The patent applies local quality by creating spatially varying bandgap regions through the superlattice structure. Each layer position has a specific bandgap tailored to its function: narrower bandgap regions (InGaAs) for photon absorption at extended wavelengths, wider bandgap regions (GaAsSb, InAlAs) for dark current suppression, creating a non-uniform bandgap profile optimized for both detection and noise reduction
Solution Approach 2:
The patent segments the detector structure into multiple functional layers with distinct bandgap characteristics. The superlattice is divided into numerous thin layers (e.g., 20-50 periods) where each layer contributes differently to the overall detection performance, allowing independent optimization of wavelength extension and dark current control in separate regions
3Measurement precision
If superlattice structure with multiple layers is implemented, then extended wavelength detection with reduced dark current is achieved, but device complexity increases
Solution Approach 1:
The patent manages complexity through systematic parameter changes rather than arbitrary design. The superlattice structure follows a repeating pattern of layer sequences (e.g., InGaAs/GaAsSb/InAlAs) with controlled variations in layer thickness and composition ratios, allowing complex functionality to be achieved through parameter optimization rather than structural complexity
Solution Approach 2:
The patent applies periodic action by implementing a repeating superlattice pattern with a fixed number of periods (e.g., 20-50 repetitions of the basic layer sequence). This periodic structure simplifies fabrication through repeated deposition cycles and allows the complex extended-wavelength detection function to be achieved through multiple identical units working in parallel
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 the detection of extended short-wave infrared wavelengths with lower dark current, improving sensitivity and operational performance at room temperature, while maintaining crystalline quality and leveraging the fabrication techniques of InGaAs-based detectors.
Implementation Method 1
A p-n junction is formed at an interface within the second superlattice structure or at an interface between the first and second superlattice structures
Implementation Method 2
The implementation of a superlattice-based detector structure with alternating layers of semiconductor materials, such as InGaAs and GaAsSb, which forms a p-n junction and graded bandgap, allowing for extended cut-off wavelengths and reduced dark current by facilitating the flow of photogenerated carriers
Data Source
AI summary
Techniques are disclosed for facilitating detection of electromagnetic radiation using superlattice-based detector systems and methods. In one example, an infrared detector includes a first superlattice structure including first periods. Each of the first periods includes a first sub-layer and a second sub-layer adjacent to the first sub-layer. The first and second sub-layers include first and second semiconductor materials. The infrared detector further includes a second superlattice structure disposed on the first superlattice structure. The second superlattice structure includes second periods. Each of the second periods includes a third sub-layer and a fourth sub-layer adjacent to the third sub-layer. The third-sub-layer includes a third semiconductor material. The fourth sub-layer includes a fourth semiconductor material. A p-n junction is formed at an interface within the second superlattice structure or at an interface between the first and second superlattice structures.