Photodetector Multi-Reset Circuit for Dark Current Suppression
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Solution Overview
Problem
Photo-detecting apparatuses face issues with leakage current and dark current, leading to increased power consumption and reduced signal-to-noise ratio, especially when used in applications like 3D imaging and LiDAR, where efficient detection of near-infrared and short-wave infrared light is required.
Innovation Solution
A photo-detecting apparatus is designed with a cascode transistor and a reset transistor, coupled with an optical-to-electric converter, which maintains a constant voltage output to suppress dark current and includes a multi-reset mechanism for improved stability and accuracy, allowing efficient detection of near-infrared and short-wave infrared light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photodetectors are used in consumer electronics products and image sensors, then light detection capability is improved, but leakage current and dark current increase leading to higher power consumption and reduced signal to noise ratio
Solution Approach 1:
The photodetector is divided into multiple independent pixel units, each with its own reset transistor and cascode transistor. This segmentation allows individual control and resetting of each pixel, enabling precise management of dark current and power consumption at the pixel level while maintaining overall detection performance
Solution Approach 2:
A reset transistor is introduced that operates before the photodetector integration period to clear accumulated charge and reset the pixel output to a known reference level. This preliminary resetting action prevents dark current accumulation from affecting the measurement signal, improving signal to noise ratio while managing power consumption through controlled resetting cycles
2Reliability
If photodetectors are used in 3D imaging and LiDAR applications, then detection of near-infrared and short-wave infrared light is improved, but leakage current and dark current degrade performance
Solution Approach 1:
A cascode transistor is introduced as an intermediary element between the photodetector and the readout circuitry. This cascode configuration acts as a buffer that isolates the photodetector from voltage fluctuations and reduces the impact of dark current on the detection signal, thereby improving reliability and detection accuracy in near-infrared and short-wave infrared applications
Solution Approach 2:
The circuit incorporates a feedback mechanism where the reset transistor is controlled by a reset signal that monitors the pixel output level. When the output approaches the reference level or exceeds a threshold, the reset transistor activates to clear the charge, creating a feedback loop that continuously manages dark current effects and maintains detection accuracy throughout the integration period
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 results in a photo-detecting apparatus with reduced dark current, lower power consumption, and higher accuracy for 3D image depth information, enabling efficient absorption of near-infrared and short-wave infrared light while maintaining a smaller chip size.
Implementation Method 1
an optical-to-electric converter, having a first output terminal, configured to convert an incident light to an electrical signal
Implementation Method 2
the light absorption material is a material different from the semiconductor substrate
Implementation Method 3
a light-absorption material formed on a semiconductor substrate, wherein the light absorption material is a material different from the semiconductor substrate
Data Source
AI summary
A photo-detecting apparatus includes an optical-to-electric converter, having a first output terminal, configured to convert an incident light to an electrical signal; a cascode transistor, having a control terminal, a first channel terminal and a second channel terminal, wherein the second channel terminal of the cascode transistor is coupled to the first output terminal of the optical-to-electric converter; and a reset transistor, having a control terminal, a first channel terminal and a second channel terminal, wherein the first channel terminal of the reset transistor is coupled to a supply voltage and the second channel terminal of the reset transistor is coupled to the first channel terminal of the cascode transistor.