APD Trench Separator Layout for Low-Voltage Pixel Crosstalk Control
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Solution Overview
Problem
Existing photoelectric conversion apparatuses with avalanche photodiodes (APDs) lack an appropriate separator structure that effectively prevents crosstalk and allows for efficient avalanche multiplication at low voltages.
Innovation Solution
The apparatus employs a trench structure separator and specific semiconductor region configurations to separate photoelectric conversion elements, utilizing a third semiconductor region of the second conductivity type to focus avalanche multiplication near the first semiconductor region, reducing crosstalk and enabling efficient charge collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a separator structure is added to prevent crosstalk between pixels, then crosstalk is reduced, but device complexity increases
Solution Approach 1:
The separator structure is nested within the existing semiconductor layer structure, utilizing the third semiconductor region that is already part of the APD device architecture. The separator is formed by extending the third semiconductor region to overlap the first semiconductor region of adjacent pixels, integrating the crosstalk prevention function into the existing device layers rather than adding separate external structures.
Solution Approach 2:
The separator structure utilizes the depth dimension (vertical overlap) between semiconductor layers to achieve crosstalk prevention. By extending the third semiconductor region vertically to overlap the first semiconductor region of adjacent pixels in the depth direction, the separator effectively blocks charge carrier movement between pixels without requiring lateral expansion or additional horizontal structures.
2Use of energy by moving object
If the avalanche multiplication region is concentrated near the first semiconductor region, then avalanche multiplication can occur at low voltage, but the depletion layer may spread excessively to deep portions
Solution Approach 1:
The third semiconductor region is configured with specific local properties (conductivity type and spatial distribution) to create localized electric field control. By positioning the third semiconductor region to overlap the first semiconductor region near the light incident surface, the electric field is concentrated in this specific region, enabling avalanche multiplication at low voltage without causing excessive depletion layer spread to deep portions of the semiconductor layer.
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 enhances the efficiency of avalanche multiplication at lower voltages while minimizing crosstalk between adjacent pixels, improving the overall performance of the photoelectric conversion apparatus.
Implementation Method 1
an avalanche multiplication region is formed by a first semiconductor region and a second semiconductor region... avalanche multiplication can be caused at low voltage
Implementation Method 2
a photoelectric conversion apparatus including an avalanche photodiode (APD)... a semiconductor layer including a plurality of photoelectric conversion elements... on which light is incident
Data Source
AI summary
An avalanche photodiode has a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type, the first semiconductor region being a region where charges having the same polarity as that of signal charges are treated as majority carriers. A separator provided between a first photoelectric conversion element and a second photoelectric conversion element has a trench structure. A top surface of the trench structure is positioned between a top surface of the second semiconductor region and a bottom surface of the second semiconductor region.