P-Type Transfer Gates for Low-Power Light Detection Pixels
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Solution Overview
Problem
Related art light detecting devices face issues with high power consumption and increased chip size due to the use of n-type transfer gates, which require negative charge pump circuits to manage dark current and electron capacity, leading to unwanted defects like image lag and white spots.
Innovation Solution
The use of p-type transfer gates, combined with a dual vertical transfer gate structure, eliminates the need for negative charge pump circuits, reducing power consumption and chip size while maintaining desired off voltage and dark current performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If n-type transfer gates are used, then electron capacity and dark current management are improved, but power consumption and chip size increase due to negative charge pump circuits
Solution Approach 1:
The patent changes the conductivity type parameter of the transfer gate from n-type to p-type, which fundamentally alters the electrical characteristics. This parameter change allows the transfer gate to achieve proper off-state voltage without requiring external charge pump circuits, thereby reducing power consumption while maintaining dark current performance through the inherent properties of p-type material in the specific device configuration
Solution Approach 2:
The invention extracts and removes the negative charge pump circuit from the device architecture. By using p-type transfer gates, the patent eliminates the need for these auxiliary power-consuming circuits while still achieving the necessary dark current management through the modified transistor characteristics and doping configuration
2Reliability
If n-type transfer gates are used, then dark current management is improved, but chip size increases due to negative charge pump circuits
Solution Approach 1:
The patent extracts and removes the negative charge pump circuit from the device architecture. By using p-type transfer gates, the invention eliminates these auxiliary circuits that occupy additional chip area, thereby reducing overall device size while maintaining dark current performance through the modified transistor characteristics
Solution Approach 2:
The invention merges the transfer gate functionality with the pixel circuit structure by using p-type transistors that can be directly integrated into the pixel array without requiring separate charge pump circuit blocks. This integration reduces the total chip area occupied by transfer gate-related components
3Reliability
If n-type transfer gates are used, then electron capacity is improved, but device complexity increases due to charge pump circuits
Solution Approach 1:
The patent removes the negative charge pump circuit from the device architecture by using p-type transfer gates. This extraction eliminates the complex auxiliary circuitry needed to manage the transfer gate off-state, thereby reducing overall device complexity while maintaining electron capacity through the inherent properties of the p-type configuration
Solution Approach 2:
The p-type transfer gate structure serves multiple functions: it provides the necessary off-state voltage control, manages dark current, and eliminates the need for separate charge pump circuits. This multi-functionality reduces device complexity by consolidating what would otherwise require multiple separate components into a single integrated structure
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 configuration achieves reduced power consumption and chip size with comparable dark current performance to n-type gates, enhancing image quality and efficiency in applications like head-mounted displays.
Implementation Method 1
a photoelectric conversion region that is disposed in a semiconductor substrate and that converts light into electric charge
Data Source
AI summary
A light detecting device includes a photoelectric conversion region that is disposed in a semiconductor substrate and that converts light into electric charge. The light detecting device includes a plurality of transistors coupled to the photoelectric conversion region. At least one transistor of the plurality of transistors has a gate having a first conductivity type while remaining ones of the plurality of transistors have gates of a second conductivity type different than the first conductivity type.