UV Sensor Photodiode Structure for Visible Light Rejection
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Solution Overview
Problem
Existing UV radiation sensors are sensitive to photons other than UV radiation, such as visible light and infrared radiation, which reduces their accuracy in detecting UV radiation.
Innovation Solution
A sensor device with a semiconductor substrate and a photodiode structure featuring two ion-implanted wells with opposite types of electrical conductivity, where the doping concentrations and profiles are adjusted to form a photon capturing layer that is predominantly sensitive to UV radiation, reducing sensitivity to visible light and infrared radiation by optimizing the p-n junction's position and carrier concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing sensors use a simple photodiode structure, then the device complexity is low and manufacturing is easy, but the sensor is sensitive to visible light and infrared radiation which reduces measurement precision for UV radiation
Solution Approach 1:
The photodiode is divided into multiple semiconductor regions with different conductivity types (first n-type region, first p-type region, second n-type region, second p-type region) arranged in alternating layers. This segmentation creates multiple internal p-n junctions that form wavelength-selective absorption zones, enabling the sensor to distinguish UV radiation from visible and infrared radiation while maintaining manageable device complexity through systematic structural repetition.
Solution Approach 2:
Different semiconductor regions are doped with specific doping concentrations tailored to their local function: the first n-type region has a first doping concentration optimized for UV absorption, while subsequent regions have different doping concentrations (second, third, fourth doping concentrations) that create varying depletion region widths and carrier generation characteristics. This local quality optimization enables each region to contribute differently to wavelength discrimination, improving UV detection precision without requiring excessive overall complexity.
2Measurement precision
If the sensor uses a single photodiode structure, then the device is simple and fast response is achieved, but parasitic photocurrent from visible and infrared radiation reduces measurement accuracy
Solution Approach 1:
The photodiode is divided into multiple semiconductor regions with different conductivity types (first n-type region, first p-type region, second n-type region, second p-type region) arranged in alternating layers. This segmentation creates multiple internal p-n junctions that form wavelength-selective absorption zones, enabling the sensor to distinguish UV radiation from visible and infrared radiation while maintaining manageable device complexity through systematic structural repetition.
Solution Approach 2:
Different semiconductor regions are doped with specific doping concentrations tailored to their local function: the first n-type region has a first doping concentration optimized for UV absorption, while subsequent regions have different doping concentrations (second, third, fourth doping concentrations) that create varying depletion region widths and carrier generation characteristics. This local quality optimization enables each region to contribute differently to wavelength discrimination, improving UV detection precision without requiring excessive overall complexity.
3Measurement precision
If deeper regions of the semiconductor substrate are utilized for photon detection, then more photons can be captured increasing sensitivity, but parasitic photocurrent from visible and infrared radiation increases reducing accuracy
Solution Approach 1:
The photodiode is divided into multiple semiconductor regions with different conductivity types (first n-type region, first p-type region, second n-type region, second p-type region) arranged in alternating layers. This segmentation creates multiple internal p-n junctions that form wavelength-selective absorption zones, enabling the sensor to distinguish UV radiation from visible and infrared radiation while maintaining manageable device complexity through systematic structural repetition.
Solution Approach 2:
The doping concentrations are systematically varied across different regions (first doping concentration in first n-type region, second doping concentration in first p-type region, third doping concentration in second n-type region, fourth doping concentration in second p-type region). This parameter change creates varying depletion region widths and carrier generation characteristics that enable wavelength discrimination, allowing deeper photon capture for UV while suppressing parasitic photocurrent from visible and infrared radiation through optimized carrier collection dynamics.
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
The sensor device achieves improved accuracy in detecting UV radiation by isolating the photon capturing layer from deeper regions, reducing parasitic photocurrent from visible and infrared radiation, and allowing for faster response times due to higher electron carrier lifetimes, thereby enhancing the measurement of UV radiation.
Implementation Method 1
a p-n junction for detecting incident ultraviolet, UV, radiation
Implementation Method 2
two ion implanted wells with opposite types of electrical conductivity
Data Source
Figure 1~3
Figure 4~6
Figure 7A~9B
AI summary
A sensor device comprises a semiconductor substrate (S) with a first type of electrical conductivity and with a photodiode structure for detecting incident UV radiation. The photodiode structure comprises a first well (W1) arranged within the semiconductor substrate (S) and having a second type of electrical conductivity and a second well (W2) arranged at least partially within the first well (W1) and having the first type of electrical conductivity. A doping concentration of the first well (W1) is greater than a doping concentration of the second well (W2) within a surface region at a main surface (MS) of the semiconductor substrate (S). Thereby, a photon capturing layer (PC) having the second type of electrical conductivity is formed at the main surface (MS). A p-n junction (PND) for detecting the incident UV radiation is formed by a boundary between the second well (W2) and the photon capturing layer (PC).