UV Photodiode Impurity Profiles for Wavelength Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing UV sensors are not sufficiently selective for UV-A and UV-B wavelengths, leading to sensitivity issues with visible and infrared light, and reducing the SOI layer thickness complicates integral circuit formation.
Innovation Solution
A solid-state light-receiving device with a semiconductor substrate featuring two non-overlapping photodiodes and a differential circuit, where the photodiodes have specific conductivity type regions and impurity concentration profiles to selectively absorb and measure UV-A and UV-B light, while minimizing sensitivity to longer wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin-film silicon-on-insulator (SOI) substrate is used to reduce sensitivity to visible and infrared light, then sensitivity to UV rays is improved, but integral formation with peripheral circuits becomes difficult
Solution Approach 1:
The patent applies local quality by creating different impurity concentration profiles in different regions of the photodiode. Specifically, the first photodiode has a first impurity concentration profile optimized for UV detection, while the second photodiode has a second impurity concentration profile that provides different spectral response characteristics. This allows each region to have tailored properties for its specific function, resolving the contradiction between UV sensitivity and circuit integration by enabling wavelength-selective detection without requiring extreme thinning of the entire SOI layer.
Solution Approach 2:
The patent changes the parameter of impurity concentration distribution within the photodiode structure. By controlling the impurity concentration profiles differently in the first and second photodiodes, the patent achieves differential spectral sensitivity. This parameter change allows the device to maintain adequate thickness for circuit integration while achieving UV-selective detection through differential measurement, thus resolving the contradiction between measurement precision and device complexity.
2Object-affected harmful factors
If the SOI layer thickness is reduced to improve UV ray selectivity, then sensitivity to visible and infrared light is reduced, but integral formation with peripheral circuits becomes difficult
Solution Approach 1:
The patent segments the photodetector function into two separate photodiodes with different impurity concentration profiles. The first photodiode is optimized for UV detection while the second photodiode provides a reference signal with different spectral characteristics. This segmentation allows the device to achieve wavelength selectivity through differential measurement rather than through extreme thinning, thus maintaining circuit integrability while reducing sensitivity to visible and infrared light.
Solution Approach 2:
By creating localized differences in impurity concentration profiles in different photodiode regions, the patent achieves spectral selectivity without requiring uniform thinning of the entire SOI layer. This allows the bulk of the substrate to remain thick enough for standard circuit fabrication processes while specific regions provide UV-selective detection capability, resolving the contradiction between harmful factor reduction and device complexity.
3Measurement precision
If bulk silicon is used as a semiconductor substrate, then sensitivity to UV rays is improved, but sensitivity to visible and infrared light increases requiring optical filters
Solution Approach 1:
The patent extracts the wavelength-selective detection function from the bulk material properties and implements it through controlled impurity concentration profiling in the photodiode structure. Instead of relying on bulk silicon's broad spectral response and adding external optical filters, the patent embeds the spectral selection capability directly in the semiconductor structure through differential impurity concentrations, thereby eliminating the need for additional optical filter components.
Solution Approach 2:
By changing the impurity concentration parameters in the photodiode structure, the patent achieves spectral response modification without requiring optical filters. The different impurity concentration profiles in the first and second photodiodes create differential absorption characteristics that selectively enhance UV detection while suppressing visible and infrared response, thus resolving the contradiction between UV sensitivity and device complexity.
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 accurate measurement of harmful UV rays with a simple structure, suitable for mobile or wearable applications, and allows for easy integration with peripheral circuits, reducing cost and size.
Implementation Method 1
a first photodiode (1) and a second photodiode (2), which are arranged so as not to three-dimensionally overlap with each other in effect
Data Source
AI summary
Provided is a solid-state light-receiving device for ultraviolet light, which is capable of measuring an irradiation amount of UV-rays, which are harmful to a human body, accurately and appropriately with a simple structure, and of being formed easily and integrally with sensors of peripheral circuits, and which is small, lightweight, low cost, and suitable for mobile or wearable applications. The solid-state light-receiving device for ultraviolet light includes a first photodiode, a second photodiode, and a differential circuit to which signals based on outputs of those photodiodes are input. The solid-state light-receiving device for ultraviolet light also includes semiconductor layer regions, which are formed in and on the above-mentioned photodiodes, and each of which includes a highest concentration position of semiconductor impurities.