Optical Sensor Visible Infrared Wavelength Separation
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Solution Overview
Problem
Existing optical sensors fail to separately tap photo currents generated by visible and infrared light effectively, leading to non-linear sensitivity issues and inefficiencies in brightness regulation and proximity detection, as they often rely on multiple sensors or non-linear combinations of wavelengths.
Innovation Solution
An optical sensor design that utilizes a p-substrate with strategically arranged active regions and doping profiles to form short-circuited pn junctions, allowing for separate tapping of photo currents from visible and infrared wavelengths at specific cathodes, with a polysilicon layer optionally used to absorb shortwave photons and enhance spectral separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single optical sensor is used to detect both visible and infrared light, then the device complexity is reduced, but the measurement precision of separate wavelength detection deteriorates
Solution Approach 1:
The sensor is segmented into multiple active regions with different doping types (n-type and p-type) arranged in alternating layers. Each region is optimized to detect specific wavelength ranges, with n-type regions detecting infrared light and p-type regions detecting visible light. This segmentation allows a single sensor structure to achieve precise wavelength separation without requiring multiple separate sensors.
Solution Approach 2:
Different regions of the sensor are given different local qualities through varying doping concentrations and types. The n-type active regions have doping profiles optimized for infrared detection, while p-type active regions have profiles optimized for visible light detection. This local differentiation enables each region to specialize in detecting its target wavelength range while maintaining overall sensor integration.
2Measurement precision
If multiple sensors are used to detect different wavelengths separately, then the measurement precision of wavelength detection is improved, but the device complexity increases
Solution Approach 1:
Multiple sensing functions are merged into a single integrated sensor structure. The alternating n-type and p-type active regions are combined in one device, allowing simultaneous detection of visible and infrared light without requiring separate sensor elements positioned side-by-side. This merging reduces device complexity while maintaining the ability to separately tap photo currents for different wavelengths.
Solution Approach 2:
The single optical sensor achieves multi-functionality by incorporating both n-type and p-type active regions that can detect different wavelength ranges. The sensor universally handles both visible and infrared light detection within one device, eliminating the need for multiple specialized sensors while maintaining detection accuracy for each wavelength range.
3Reliability
If no spectral filtering is applied, then the sensitivity of the sensor is improved, but the ability to separate visible and infrared photo currents deteriorates
Solution Approach 1:
The sensor utilizes parameter changes in the doping profiles of active regions to achieve spectral separation without external filters. By varying doping concentrations and types (n-type vs p-type) in different active regions, the sensor creates distinct photo current responses to different wavelengths. This allows the sensor to maintain high sensitivity while achieving precise spectral separation through electrical rather than optical means.
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 achieves high collection efficiency and spectral separation of photo currents, ensuring that only relevant wavelengths contribute to the sensor output, mimicking human eye sensitivity and improving brightness regulation and proximity detection.
Implementation Method 1
Photo currents generated by light in the visible wavelength range and light in the infrared wavelength range may be tapped separately at pn junctions of active regions
Implementation Method 2
a first type of doping that decreases in the depth of the sensor and a second type of doping that increases in the depth of the sensor, wherein the first doping and the second doping form a pn junction
Data Source
AI summary
An optical sensor in which photo currents generated by light in the visible and infrared wavelength ranges are to be tapped separately at pn junctions of active regions. The active regions include n- or p-doping and are formed in a p-substrate 52. The optical sensor comprises a surface-near first active region 12, and a second active region 14 subjacent to the first active region 12 and forming together with the first active region 12 a pn junction 22 that is short-circuited. A third active region 20 is subjacent to the second active region 14 and forming together with the second active region a further pn junction 23. Together with a fourth active region 24 subjacent to the second active region 20, a further pn junction 25, 29 is formed together with the third active region 20 and the substrate 52.