Buried Electrode Photodetection for Deep Charge Resolution
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Solution Overview
Problem
Conventional photodetection devices face challenges in detecting electric charges generated in deep portions of semiconductor substrates efficiently, leading to longer detection times and reduced time resolution due to the diffusion of charges to the PN junction region.
Innovation Solution
A photodetection device with a buried portion that includes an electrode and a dielectric member, positioned deeper than the PN junction, which facilitates faster charge detection by creating an inversion layer that allows electric charges to undergo avalanche amplification without reaching the surface PN junction, thereby reducing the time required for detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electric charges are generated in deep portions of the semiconductor substrate, then photoelectric conversion can occur, but the detection time increases due to diffusion to the PN junction region
Solution Approach 1:
The invention introduces a vertical dimension by placing the buried portion at a depth between the PN junction and the back surface of the semiconductor substrate. This three-dimensional spatial arrangement creates a new detection pathway that operates independently from the traditional surface-level PN junction, enabling simultaneous detection of charges from different depths with distinct time characteristics.
Solution Approach 2:
The photodetection function is segmented into two independent systems: the surface PN junction for detecting charges generated near the surface, and the buried portion for detecting charges generated in deep portions. Each segment operates autonomously with its own detection mechanism, allowing differentiated handling of charges based on their generation location and reducing overall detection time by parallel processing.
2Speed
If the PN junction is positioned at the surface for efficient charge detection, then detection speed improves, but charges generated in deep portions take longer to reach the junction via diffusion
Solution Approach 1:
The buried portion acts as an intermediary detection point for charges generated in deep portions of the substrate. Instead of requiring charges to diffuse all the way from deep regions to the surface PN junction, the buried portion provides an intermediate collection point closer to the charge generation region, thereby reducing transport time while maintaining efficient detection capability.
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 proposed solution significantly reduces the time needed to detect electric charges generated in deep portions of the semiconductor substrate, improving time resolution and minimizing the dispersion in detection times between surface and deep-generated charges.
Implementation Method 1
a photocarrier generated from a single photon triggers avalanche amplification in a PN junction region
Implementation Method 2
configured to perform photoelectric conversion
Data Source
AI summary
A semiconductor substrate has a first surface and a second surface which is opposite to the first surface. A photoelectric conversion portion has a PN junction configured with first and second semiconductor regions of different conductivity types. A buried portion is buried in the semiconductor substrate and includes an electrode and a dielectric member located between the electrode and the semiconductor substrate and in contact with the second semiconductor region. The second semiconductor region is located in a position deeper than the first semiconductor region. The buried portion is located to extend from a first surface to a position deeper than the first semiconductor region. Electric potentials are supplied to the first semiconductor region, the second semiconductor region, and the electrode in such a manner that an inversion layer occurring between the electrode and the second semiconductor region and the first semiconductor region are in contact with each other.