Open Circuit Voltage Photodetector Dark Current Suppression
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Solution Overview
Problem
Existing infrared sensing and imaging technologies face challenges with high dark currents, which are difficult to reduce without cooling, leading to increased system costs and barriers to widespread adoption.
Innovation Solution
The implementation of an open circuit voltage photodetector (VocP) that uses a photovoltaic device connected to a MOS transistor, generating an open circuit voltage proportional to illumination, which modulates the channel current, reducing noise and enabling low-cost, room-temperature operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current generation photodetectors are used for infrared sensing, then the photocurrent can be readily detected, but high levels of dark current are generated
Solution Approach 1:
The patent introduces an intermediary transistor between the photodetector and the readout circuitry. The photodetector generates a voltage signal in response to incident radiation, and this voltage modulates the gate of the transistor, which then controls the channel current. This intermediary transistor configuration allows the system to detect radiation while significantly reducing the harmful dark current that directly flows in conventional photodetector circuits.
2Object-generated harmful factors
If temperature is significantly reduced to cryogenic levels, then dark current is reduced, but system cost and complexity increase
Solution Approach 1:
The patent replaces the mechanical/thermal approach (cryogenic cooling systems) with an electrical/electronic solution (transistor-based voltage modulation circuit). Instead of using complex cooling machinery to reduce dark current, the invention uses the transistor's voltage-controlled channel to achieve dark current suppression while maintaining room temperature operation, thereby eliminating the need for costly cooling infrastructure.
3Object-generated harmful factors
If voltage modulation is used instead of direct current generation, then dark current is reduced, but integration with standard CMOS technology becomes more challenging
Solution Approach 1:
The patent designs the transistor and circuit configuration to serve multiple functions simultaneously: it acts as both the readout amplifier and the dark current suppression mechanism. The same transistor that amplifies the photodetector's voltage signal also inherently blocks dark current through its voltage-controlled channel properties. This multi-functionality ensures compatibility with standard CMOS fabrication processes while achieving dark current reduction.
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 VocP design achieves reduced noise and linear photocurrent response, compatible with standard silicon CMOS technology, facilitating low-cost, room-temperature infrared sensing and imaging without the need for cooling.
Implementation Method 1
an open circuit voltage is generated in a photovoltaic device in response to illumination by incident radiation
Implementation Method 2
the open circuit voltage is applied to a gate terminal of a transistor to modulate a channel current flowing in a channel of the transistor
Data Source
AI summary
An open circuit voltage photodetector comprises a photovoltaic device including a photovoltaic junction, and a transistor. The photovoltaic device is connected to the gate terminal of the transistor to input an open circuit voltage of the photovoltaic device to the gate terminal. An array of such photodetectors and a readout integrated circuit forms an image sensor. In a photodetection method, an open circuit voltage is generated in a photovoltaic device in response to illumination by incident radiation, and the open circuit voltage is applied to a gate terminal of a transistor to modulate a channel current flowing in a channel of the transistor. A readout electronic circuit may be fabricated with an extra transistor, and a photovoltaic device disposed on the readout electronic circuit and electrically connected to apply an open circuit voltage of the photovoltaic device to a gate of the extra transistor.