Photodiode Pixel With Annular Diffused Area for Low Noise
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Solution Overview
Problem
Conventional photodiode array pixels contribute to high dark current and capacitance, which negatively impact signal-to-noise ratios in cameras due to their design.
Innovation Solution
A photodiode pixel design featuring an annular diffused area in the cap layer extending into the absorption layer, utilizing a p-type material and a dielectric material layer to reduce dark current and capacitance, while maintaining optical signal detection capabilities across a wide wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel designs are used in photodiode arrays, then the structure is simple and easy to manufacture, but dark current and capacitance are high, leading to poor signal-to-noise ratio
Solution Approach 1:
The pixel structure is segmented into distinct functional regions: an absorption layer for photon detection, a cap layer for passivation, and an annular diffused area for charge collection. This segmentation allows each region to be optimized independently, reducing dark current and capacitance while maintaining manufacturing feasibility through standardized layering processes.
Solution Approach 2:
The annular diffused area is strategically positioned at the interface between the cap layer and absorption layer, creating a localized region with enhanced electrical properties. This local modification concentrates the charge collection function in a specific geometry that minimizes capacitance while maintaining effective photon detection across the broader pixel area.
2Measurement precision
If the pixel area is increased to improve signal detection, then more photons are detected, but dark current and capacitance increase proportionally
Solution Approach 1:
The pixel structure is segmented into distinct functional regions: an absorption layer for photon detection, a cap layer for passivation, and an annular diffused area for charge collection. This segmentation allows each region to be optimized independently, reducing dark current and capacitance while maintaining manufacturing feasibility through standardized layering processes.
Solution Approach 2:
The cap layer acts as an intermediary between the absorption layer and the external environment, providing passivation that reduces surface-generated dark current. This intermediate layer allows the pixel to maintain a larger absorption area for photon detection while isolating the sensitive junction from sources of noise.
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 design effectively minimizes dark current and capacitance, leading to lower noise and improved signal-to-noise ratios in camera systems without compromising absorption capabilities.
Implementation Method 1
The absorption layer can be a semiconductor material able to detect optical signals from a light source through wavelengths ranging from the ultraviolet region to the long-wave infrared region
Implementation Method 2
The cap layer can be matched to the absorption layer and can have a wider bandgap material lattice than the absorption layer to provide passivation of the absorption layer
Implementation Method 3
The pixel has an annular diffused area to reduce dark current and capacitance
Data Source
AI summary
A photodiode has an absorption layer and a cap layer operatively connected to the absorption layer. A pixel is formed in the cap layer and extends into the absorption layer to receive charge generated from photons therefrom. The pixel defines an annular diffused area to reduce dark current and capacitance. A photodetector includes the photodiode. The photodiode includes an array of pixels formed in the cap layer. At least one of the pixels extends into the absorption layer to receive charge generated from photons therefrom. At least one of the pixels defines an annular diffused area to reduce dark current and capacitance.