Photodiode Doping Structure for Faster Charge Transfer
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Solution Overview
Problem
Large-scale photodiodes face challenges in achieving fast and efficient charge transfer due to increased charge transport distance, leading to long internal charge transfer times and low efficiency, particularly in high-speed, low-noise imaging applications, where current methods are complex and costly.
Innovation Solution
A novel photodiode structure with a substrate, functional doping area, surface doping area, and auxiliary doping area, featuring non-uniform doping concentrations to create a potential gradient, accelerating charge transfer and enhancing collection efficiency, while reducing manufacturing complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the photodiode dimension is increased to improve signal-to-noise performance, then the signal strength is improved, but the charge transfer time increases and transfer efficiency decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping concentration distribution within the photodiode structure. Specifically, the doping concentration varies spatially to form an internal electric field that accelerates charge carriers in regions where it is most needed, thereby improving charge transfer efficiency without requiring a reduction in device size. This localized optimization of electrical properties resolves the contradiction between maintaining large dimensions for signal strength and achieving fast charge transfer.
Solution Approach 2:
The patent changes the doping concentration parameter from uniform to non-uniform distribution. By modifying the doping profile, an internal electric field is generated that enhances charge carrier drift velocity. This parameter change enables faster charge transfer in large-scale photodiodes, resolving the time loss issue while maintaining the beneficial signal-to-noise performance of larger devices.
2Speed
If conventional doping techniques are used to improve charge transfer speed, then charge transfer speed increases, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent merges the formation of the doping structure and the generation of the electric field into a single non-uniform doping process. Instead of using multiple separate steps (multiple masks for different doping levels), the invention achieves both structural formation and field generation through one integrated doping approach, significantly reducing manufacturing complexity while maintaining high charge transfer speed.
Solution Approach 2:
The patent extracts the essential function of generating an electric field from the complex multi-step doping process. By using a single non-uniform doping structure to create the internal electric field, the invention removes the need for multiple additional masks and complex processing steps, thereby reducing manufacturing complexity while preserving the charge transfer speed enhancement.
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 novel structure improves internal charge transfer speed and photo-generated charge collection efficiency, reducing noise and manufacturing costs, thus addressing the limitations of existing large-scale photodiode technologies.
Implementation Method 1
The functional doping area has a non-uniform doping concentration distribution to form a potential gradient in the functional doping area
Implementation Method 2
Charge transfer is based on a complex process driven by various coupling processes, including drift, diffusion, and self-induced drift
Implementation Method 3
Charge transfer is based on a complex process driven by various coupling processes, including drift, diffusion, and self-induced drift
Implementation Method 4
Photodiodes are semiconductor devices that respond to high-energy particles and photons by absorbing the photons or high-energy particles and outputing a current proportional to the incident power to an external circuit
Data Source
AI summary
A novel photodiode structure, a preparation method and a circuit structure are provided. The novel photodiode structure includes a substrate having a first doping type, a functional doping area having a second doping type, a surface doping area having the first doping type, and an auxiliary doping area having the second doping type. By forming a non-uniformly doped functional doping area, the present disclosure forms a self-built potential difference in the functional doping area and drives the moving direction of the photogenerated carriers. The photogenerated carriers may be accelerated by the potential difference, so that the collected carriers will directly enter the subsequent circuit through the transport gate. In addition, the loop shape of the auxiliary doping area can increase the area of receiving charges, in a result, the auxiliary doping area can receive the transported carriers faster, thereby further enhancing the transport efficiency of the photogenerated carriers.