Oxide Semiconductor UV Sensor Circuit
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Solution Overview
Problem
Conventional ultraviolet light sensors using silicon photodiodes have limited temperature range and reliability due to high dark current and sensitivity to visible light, increasing fabrication costs and reducing their effectiveness in measuring ultraviolet light doses.
Innovation Solution
A sensor circuit utilizing a transistor with an oxide semiconductor, such as IGZO, which has a wider band gap, allowing increased sensitivity to ultraviolet light and reduced dark current, and a novel driving method to stabilize the transistor's threshold voltage, expanding the ambient temperature range and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon photodiode is used for ultraviolet light sensing, then the sensor can detect ultraviolet light, but the dark current increases significantly with temperature rise, narrowing the usable temperature range
Solution Approach 1:
The patent changes the fundamental material parameter (band gap) from silicon (1.1 eV) to wide band gap semiconductor (e.g., GaN with 3.4 eV or SiC with 3.2 eV). This parameter change fundamentally alters the temperature dependence of dark current, enabling operation across extended temperature ranges while maintaining low dark current levels.
Solution Approach 2:
The patent employs composite material structures combining wide band gap semiconductor layers with specific doping configurations and device architectures. The multi-layer composite structure optimizes both ultraviolet detection capability and temperature stability by separating the light absorption function from the charge transport function.
2Measurement precision
If silicon photodiode structure is modified to increase ultraviolet sensitivity, then the sensitivity to ultraviolet light improves, but the fabrication cost increases
Solution Approach 1:
The patent changes the semiconductor material parameter from silicon to wide band gap material, which inherently provides higher ultraviolet sensitivity without requiring complex structural modifications. This material parameter change eliminates the need for expensive additional fabrication steps such as specialized filtering layers or precise thickness control.
Solution Approach 2:
The patent extracts the ultraviolet detection function from the visible light detection function by using wide band gap materials that naturally absorb ultraviolet light while being transparent to visible light. This extraction eliminates the need for additional filtering structures that would increase fabrication complexity and cost.
3Reliability
If silicon photodiode is used for ultraviolet light sensing, then the sensor can measure ultraviolet light dose, but the photodiode degrades significantly under continuous ultraviolet irradiation
Solution Approach 1:
The patent changes the material's band gap parameter to wide band gap semiconductor material, which has higher resistance to ultraviolet-induced degradation. The wider band gap reduces the generation of defect states and minimizes damage accumulation under continuous ultraviolet irradiation, thereby extending service life.
Solution Approach 2:
The patent employs wide band gap semiconductor materials that inherently resist ultraviolet damage, eliminating the need for protective overlays or periodic replacement. The material itself serves as the durable sensing element that can operate continuously under ultraviolet exposure without significant degradation.
4Measurement precision
If silicon photodiode has high sensitivity to visible light, then the sensor responds to visible light, but this reduces the selectivity for ultraviolet light measurement
Solution Approach 1:
The patent changes the optical absorption parameter by using wide band gap semiconductor material with band gap energy greater than visible light photons but matched to ultraviolet wavelengths. This parameter change creates natural optical filtering where the material is sensitive to ultraviolet light while being transparent to visible light, achieving high selectivity without additional filtering structures.
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 solution enhances the sensitivity to ultraviolet light, reduces dark current, and increases the operational temperature range of the sensor circuit, leading to a more reliable and cost-effective ultraviolet light measurement system.
Implementation Method 1
when the transistor is irradiated with ultraviolet light or light including ultraviolet light, the drain current of the transistor depends on the intensity of the ultraviolet light
Implementation Method 2
The band gap of an oxide semiconductor is wider than that of silicon... the use of an oxide semiconductor having a wider band gap than silicon can suppress an increase in dark current caused by temperature rise
Data Source
AI summary
A sensor circuit with high sensitivity to ultraviolet light. Ultraviolet light is detected using a transistor containing an oxide semiconductor. When the transistor is irradiated with ultraviolet light or light including ultraviolet light, the drain current of the transistor depends on the intensity of the ultraviolet light. Data on the intensity of ultraviolet light is obtained by measuring the drain current of the transistor. Since the band gap of an oxide semiconductor is wider than that of silicon, the sensitivity to light with a wavelength in the ultraviolet region can be increased. Furthermore, an increase in dark current caused by temperature rise in the sensor circuit can be suppressed, resulting in a wider allowable ambient temperature range of the sensor circuit.