Wavelength Selective Radiation Sensor Using Segmented PN Junctions
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Solution Overview
Problem
Current UV sensors, particularly silicon sensors and GaN sensors, are ineffective in selectively measuring UV light intensity across UVA, UVB, and UVC bands due to UV blocking layers and shallow absorption depth, and are not cost-effective for analyzing UV radiation composition.
Innovation Solution
A radiation sensor design featuring multiple semiconductor regions with a sensing PN junction and a draining PN junction, where the bias circuit maintains a fixed sensing PN junction depletion region while varying the size of the draining PN junction depletion region to distinguish between different wavelengths, allowing for selective sensitivity to UV radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If silicon sensors are used for UV detection, then visible light detection capability is improved, but UV detection response is weakened due to UV blocking layers and shallow absorption depth
Solution Approach 1:
The sensor is divided into multiple semiconductor regions with different bandgap energies, where each region is optimized for detecting specific UV wavelength bands (UVA, UVB, UVC). This segmentation allows simultaneous optimization for both UV detection and visible light detection without mutual interference, as each region independently processes its designated wavelength range.
Solution Approach 2:
Different semiconductor materials or doped regions are used at different locations within the sensor structure to create local variations in absorption characteristics. The UV-sensitive regions use materials optimized for UV absorption while visible light regions maintain silicon's natural properties, enabling each local area to excel at its specific detection task.
2Measurement precision
If GaN sensors are used for visible-blind UV detection, then UV detection selectivity is improved, but cost increases and UV composition analysis capability deteriorates
Solution Approach 1:
The sensor divides UV detection into multiple wavelength-specific regions, each optimized for a particular UV band. This allows the use of cost-effective silicon-based materials while achieving wavelength-selective UV detection through structural design rather than requiring expensive alternative materials for each wavelength band.
Solution Approach 2:
The invention changes the structural parameters of the semiconductor regions (such as doping concentrations, layer thicknesses, and junction depths) to tune the absorption characteristics for different UV wavelengths. This enables wavelength-selective detection using standard silicon processing techniques, avoiding the need for expensive GaN materials while maintaining UV selectivity and composition analysis capability.
3Ease of manufacture
If standard silicon sensors are used, then manufacturing cost is reduced, but UV wavelength differentiation capability is lost due to shallow absorption depth
Solution Approach 1:
The silicon sensor is segmented into multiple regions with different depths and doping profiles, allowing each region to respond to UV wavelengths that penetrate to different depths. This enables wavelength differentiation using standard silicon materials and manufacturing processes, eliminating the need for expensive alternative materials while recovering the lost UV spectral analysis capability.
Solution Approach 2:
The invention introduces depth as an additional dimension for wavelength discrimination, creating vertical gradients in doping concentration and junction depth. This allows different UV wavelengths to be detected at different depths within the silicon structure, enabling spectral analysis without requiring multiple separate sensors or expensive specialized materials.
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 design enables accurate differentiation between UV wavelengths by controlling depletion region sizes, reducing dependence on process variations and providing cost-effective, radiation-selective measurement capabilities.
Implementation Method 1
Ultraviolet (UV) sensors are used for measuring UV light intensity
Implementation Method 2
Silicon sensors have very shallow absorption depth in the UV range
Data Source
AI summary
There may be provided a radiation sensor, that may include multiple semiconductor regions that form a sensing PN junction and a draining PN junction that is located below the sensing PN junction; a bias circuit that is configured to (i) bias the sensing PN junction to maintain a sensing PN junction depletion region of a fixed size during a first sensing period and during a second sensing period, and (i) bias the draining PN junction to form a draining PN junction depletion region of a first size during the first sensing period and of a second size during the second sensing period; and an output circuit that is configured to generate a first output signal that represent sensed radiation out of radiation that impinged on the radiation sensor during the first sensing period, and to generate a second output signal that represent sensed radiation out of radiation impinged on the radiation sensor during the second sensing period.