Shielded Photodiode Layout for High-SNR Low-Power Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current photodiodes, such as single photon avalanche diodes (SPADs) and dynamic photodiodes (DPDs), face challenges in achieving high signal-to-noise ratio (SNR) with low power consumption and efficient quantum detection, particularly in consumer applications like time-of-flight sensors and photoplethysmography devices, due to limitations in quantum efficiency, noise, and dark current issues.
Innovation Solution
The design of a photodiode with decoupled absorption and amplification regions, where the amplification region is shielded from light absorption using a metal shielding layer, allowing for increased quantum efficiency and minimized noise, and enabling multiple channels with different spectral sensitivities integrated into a single device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplification region is exposed to radiation to be detected, then charge carriers can be generated for signal detection, but noise increases and quantum efficiency decreases due to direct absorption in the amplification region
Solution Approach 1:
The photodiode structure is segmented into distinct functional regions: a first doped area for charge carrier generation, a second doped area for signal amplification, and an intrinsic region separating them. This spatial segmentation allows the amplification region to be shielded from direct radiation exposure while still functioning effectively.
Solution Approach 2:
The harmful function of direct radiation absorption in the amplification region is extracted and removed by introducing a radiation shield between the light entrance side and the second doped area. This isolates the amplification region from harmful radiation exposure.
2Power
If single photon avalanche diodes (SPADs) are used to achieve high gain, then signal amplification is improved, but power consumption increases and they do not meet low power consumption requirements
Solution Approach 1:
The photodiode operates in a linear mode with controlled biasing rather than avalanche breakdown mode. By adjusting the doping concentrations and bias voltages, the device achieves optimized signal amplification at low power consumption, avoiding the high voltage requirements of SPADs.
3Use of energy by moving object
If dynamic photodiodes (DPDs) are used for low power consumption, then energy efficiency is improved, but quantum efficiency is limited and signal-to-noise ratio decreases
Solution Approach 1:
Different regions of the photodiode are optimized for different functions: the first doped area is optimized for high quantum efficiency with appropriate doping concentration and geometry for effective charge carrier generation, while the second doped area is optimized for signal amplification. This local optimization allows both high quantum efficiency and low power consumption to be achieved simultaneously.
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 design enhances quantum efficiency, minimizes dark current, and improves SNR across a wide range of conditions, enabling efficient low-power operation with tailored absorption characteristics for specific spectral regions, suitable for consumer applications.
Implementation Method 1
The second doped area is configured to absorb radiation to be detected and therefore to generate charge carriers
Implementation Method 2
The radiation shield covers and shields the first doped area from the radiation to be detected
Data Source
AI summary
In an embodiment a photodiode includes a semiconductor body having a light entrance side and a back side opposite the light entrance side, a first electrode at the light entrance side atop a first doped area of a first conductivity type, a second electrode at the light entrance side atop a second doped area of a second conductivity type, the second doped area being configured to absorb radiation, a gate region at the light entrance side at least between the first electrode and the second electrode, the gate region being connected to a gate electrode, a base electrode at the semiconductor body, the base electrode being configured to receive a current flow from the first electrode, the current flow being indicative of a radiant flux of the radiation onto the second doped area and a radiation shield covering and shielding the first doped area from the radiation to be detected.