Two-Terminal Multi-Mode Detector Stack for Simplified Imaging
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Solution Overview
Problem
Conventional imaging systems require multiple focal plane arrays, readout ICs, and complex optics to achieve high performance across various spectral bands, leading to increased cost and reliability issues.
Innovation Solution
A two-terminal multi-mode detector with a back-to-back p/n/p SWIR/MWIR detector stack structure, grown epitaxially using MBE, allowing for co-located and near-simultaneous MWIR thermal imaging, high-resolution eye-safe LADAR, and large dynamic range active/passive detection in the VIS-SWIR spectral regions, without the need for multiple image planes or complex optics, utilizing a wide bandgap barrier layer and HgCdTe layers with CdTe passivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple focal plane arrays, readout ICs, and complex optics are used to achieve high performance across various spectral bands, then imaging performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple spectral detection capabilities (MWIR, SWIR, and visible bands) into a single focal plane array using a stacked p/n/p detector architecture. This merging of multiple detection functions into one device eliminates the need for separate focal plane arrays and complex optics, directly resolving the contradiction between imaging performance and system complexity
Solution Approach 2:
The detector stack is designed to perform multiple imaging functions simultaneously across different spectral bands. The p/n/p structure enables the same device to detect MWIR, SWIR, and visible radiation, providing universal multi-functional capability that improves reliability while reducing the number of components needed
2Adaptability or versatility
If multiple focal plane arrays and readout ICs are used to cover various spectral bands, then spectral coverage is improved, but manufacturing cost increases
Solution Approach 1:
Multiple spectral detection capabilities are merged into a single detector stack structure, eliminating the need to manufacture and assemble multiple separate focal plane arrays and readout ICs. This single-device approach significantly reduces manufacturing complexity and cost while maintaining broad spectral coverage
Solution Approach 2:
The detector provides universal spectral coverage across MWIR, SWIR, and visible bands through its stacked p/n/p architecture, replacing multiple specialized detectors. This multi-functional design reduces the total number of components that need to be manufactured and integrated, thereby lowering overall manufacturing cost
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
Enables high-performance imaging across multiple spectral bands in a single focal plane, reducing complexity and cost while maintaining reliability, with the ability to switch between imaging modes by controlling bias voltage polarity and amplitude.
Implementation Method 1
when a positive bias of a predetermined magnitude is applied to the top of the stack such that the junction between the P-MWIR layer and the N-MWIR absorber layer is forward-biased and the junction between the P-SWIR absorber layer and the N-SWIR layer is reverse-biased, the detector collects photocurrent from SWIR radiation
Implementation Method 2
when a negative bias of a predetermined magnitude is applied to the top of the stack such that the junction between the P-MWIR layer and the N-MWIR absorber layer is reverse-biased and the junction between the P-SWIR absorber layer and the N-SWIR layer is forward-biased, the detector collects photocurrent from MWIR radiation
Implementation Method 3
applying a positive bias of predetermined magnitude to the top of the stack induces electron avalanche at the junction between the P-SWIR absorber layer and the N-SWIR layer, such that the detector's sensitivity is sufficient to provide LLL passive amplified imaging
Data Source
AI summary
A two-terminal detector has a back-to-back p/n/p SWIR/MWIR stack structure, which includes P-SWIR absorber, N-SWIR, wide bandgap bather, N-MWIR absorber, and P-MWIR layers, with contacts on the P-MWIR and P-SWIR layers. The junction between the SWIR layers and the junction between the MWIR layers are preferably passivated. The detector stack is preferably arranged such that a negative bias applied to the top of the stack reverse-biases the MWIR junction and forward-biases the SWIR junction, such that the detector collects photocurrent from MWIR radiation. A positive bias forward-biases the MWIR junction and reverse-biases the SWIR junction, such that photocurrent from SWIR radiation is collected. A larger positive bias induces electron avalanche at the SWIR junction, thereby providing detector sensitivity sufficient to provide low light level passive amplified imaging. Detector sensitivity in this mode is preferably sufficient to provide high resolution 3-D eye-safe LADAR imaging.