Infrared Detector Using Silver-Silicon Schottky Barriers
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Solution Overview
Problem
Current infrared external photoemissive detectors are limited to detecting wavelengths no longer than 2µm due to heterojunction barriers and require ultra-high vacuum conditions for maximum sensitivity, making them impractical for detecting radiation beyond 2µm and unsuitable for extended atmospheric exposure.
Innovation Solution
An external photoemissive infrared detector using a silver n-type silicon composite with an n-p heterojunction, where the n-layer is doped silicon embedded with silver nanoparticles forming Schottky barriers and a p-type diamond film with a negative electron affinity surface, allowing detection of wavelengths beyond 2µm under modest vacuum conditions and atmospheric exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photocathodes with heterojunction barriers are used, then detection sensitivity is improved, but wavelength detection is limited to no longer than 2μm
Solution Approach 1:
The patent uses a composite structure consisting of an n-type semiconductor layer with embedded metal nanoparticles (forming Schottky barriers) combined with a p-type diamond film layer. This composite heterojunction structure enables detection of wavelengths beyond 2μm while maintaining detection sensitivity, overcoming the limitation of conventional single-material photocathodes.
Solution Approach 2:
The invention introduces metal nanoparticles at specific locations within the n-type semiconductor layer to create localized Schottky barriers. These localized regions with different electrical properties enable the structure to detect longer wavelengths while maintaining overall detection efficiency.
2Measurement precision
If ultra-high vacuum conditions are used for maximum sensitivity, then detection performance is improved, but manufacturing complexity and operational requirements worsen
Solution Approach 1:
The p-type diamond film layer acts as a protective barrier that allows the detector to operate in atmospheric conditions without compromising the sensitivity of the underlying n-type semiconductor layer. This eliminates the requirement for ultra-high vacuum environments while maintaining detection performance.
3Ease of manufacture
If conventional photocathode structures are used, then manufacturing is simplified, but the device cannot detect radiation beyond 2μm
Solution Approach 1:
The patent combines n-type semiconductor material with metal nanoparticles and p-type diamond film to create a composite structure that maintains manufacturing feasibility while enabling detection of wavelengths beyond 2μm, thus improving wavelength detection capability without excessive manufacturing complexity.
4Device complexity
If a single film of material is used to detect multiple atmospheric windows, then device complexity is reduced, but manufacturing precision requirements worsen
Solution Approach 1:
The invention utilizes changes in doping concentration and metal nanoparticle distribution within the n-type semiconductor layer to create different response characteristics for different wavelength ranges. This allows a single film structure to detect multiple atmospheric windows (1-2μm, 3-5μm, and 8-14μm) by optimizing the electrical parameters rather than requiring multiple separate layers.
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 efficient detection of radiation across multiple atmospheric windows (1-2µm, 3-5µm, and 8-14µm) with reduced manufacturing complexity and no need for toxic materials, maintaining operational integrity in atmospheric conditions.
Implementation Method 1
External photoemitters (or photocathodes) are known in the art as a means to detect optical radiation
Implementation Method 2
the n-layer semiconductor comprising doped silicon embedded with nanoparticles forming Schottky barriers
Implementation Method 3
The p-layer is a p-type diamond film with a negative electron affinity surface layer
Data Source
Figure 1
AI summary
An infrared external photoemissive detector can have an n-p heterojunction comprising an n-type semiconductor layer and a p-layer; the n-layer semiconductor comprising doped silicon embedded with nanoparticles forming Schottky barriers; and the p-layer is a p-type diamond film. The nanoparticles can be about 20 - 30 atomic percentage metal particles (such as silver) having an average particle size of about 5 - 10 nm. The p-layer can have a surface layer that has a negative electron affinity. The n-layer can be in the range of about 3 µm to 10 µm thick, and preferably about 3 µm thick. The doped silicon can be doped with elements selected from the list consisting of phosphorus and antimony.