Optical Sensor Gate Electrode Carrier Concentration
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Solution Overview
Problem
Conventional optical sensors using PN junction or MOS structures face issues with sensitivity and wavelength dependence due to light absorption in semiconductor and electrode layers, leading to decreased sensitivity and increased wavelength dependence.
Innovation Solution
An optical sensor comprising a transistor with a gate electrode having a carrier concentration of 1.0×10^14/cm^3 to 1.0×10^17/cm^3, an active layer forming a channel with the same type of carriers, source and drain electrodes, and a gate insulating film, where light intensity is detected by changes in current flowing between the source and drain electrodes when light is irradiated onto the gate electrode's depletion layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional photoelectric conversion elements use semiconductor layers and electrode layers for light transmission, then the structure is simple and manufacturing is easy, but light with short-wavelengths is absorbed in these layers causing decreased sensitivity and increased wavelength dependence
Solution Approach 1:
The invention extracts the light detection function from the conventional PN junction or MOS structure and relocates it to a separate photodiode element. This allows the transistor to function purely as a signal amplifier while the photodiode handles light absorption, eliminating the problem of light absorption in the transistor's semiconductor and electrode layers.
Solution Approach 2:
The invention merges the photodiode and transistor into a single integrated optical sensor structure. The photodiode generates photocurrent from incident light, and the transistor amplifies this signal, combining light detection and signal amplification functions in one device while avoiding the wavelength dependence issue.
2Reliability
If conventional photoelectric conversion elements use PN junction or MOS structure with depletion layer exposure to light, then the basic photoelectric conversion function is achieved, but sensitivity is limited and wavelength dependence increases
Solution Approach 1:
The invention introduces the transistor as an intermediary component between the light source and the signal output. The photodiode converts light to electrical signal, and the transistor amplifies this signal before output. This intermediary amplification stage significantly enhances sensitivity while maintaining the basic photoelectric conversion function.
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 configuration significantly improves sensitivity and reduces wavelength dependence, allowing for high-quality optical sensor arrays with increased numerical aperture and density, while simplifying manufacturing and reducing costs.
Implementation Method 1
intensity of irradiated light is detected by a change in a value of current flowing between the source electrode and the drain electrode when the light is irradiated onto a depletion layer formed at the gate electrode
Data Source
AI summary
An optical sensor that is a transistor which includes a gate electrode including a semiconductor material where the carrier concentration is 1.0×1014/cm3 to 1.0×1017/cm3, an active layer including a semiconductor layer to form a channel by carriers of the same type as the gate electrode, a source electrode, a drain electrode, and a gate insulating film, wherein intensity of irradiated light is detected by a change in a value of current flowing between the source electrode and the drain electrode when the light is irradiated onto a depletion layer formed in the gate electrode; an optical sensor array, an optical sensor driving method, and an optical sensor array driving method are provided.