Radiation Detector Anode Biasing for Charge Collection Control
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Solution Overview
Problem
Pixelated radiation detectors face inefficiencies in charge collection due to surface recombination in gaps between anodes and incomplete recovery of shared events with signals below the electronic threshold, leading to noise increase and deteriorated energy resolution.
Innovation Solution
A charge collection control arrangement using switches and resistors forming a voltage divider is implemented to bias anodes, shifting the charge sharing line within the semiconductor substrate, thereby directing charges towards anodes and minimizing surface recombination, allowing for complete charge collection even for events below the threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the summing method is used to improve charge collection, then the charge collection efficiency is improved, but the noise (energy resolution) increases
Solution Approach 1:
The patent applies local quality by creating non-uniform electric fields through biasing adjacent anodes at different potentials. This causes the charge sharing line to shift locally towards the center of the pixel, ensuring that charges are collected by the intended anode rather than being shared with adjacent anodes. This local field modification improves charge collection efficiency without requiring signal summing, thereby maintaining energy resolution.
2Reliability
If adjacent anodes are biased to improve charge collection, then charge sharing is reduced, but device complexity increases
Solution Approach 1:
The patent employs dynamic biasing where the polarity of the bias voltage applied to adjacent anodes is reversed depending on the direction of charge sharing. When charges tend to share with the right adjacent anode, the right anode is biased positively; when charges tend to share with the left adjacent anode, the left anode is biased positively. This dynamic adjustment optimizes charge collection efficiency while managing the complexity through controlled, directional biasing.
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 solution reduces surface recombination, recovers all shared events, maintains energy resolution, and enhances detector sensitivity, enabling the use of multiple isotopes and improving manufacturing yields.
Implementation Method 1
The electrons drift toward the positively biased pixelated anodes and the holes drift toward the negatively biased cathode
Implementation Method 2
the surface recombination in the gap between the anodes
Implementation Method 3
A charge collection control arrangement having a plurality of switches and resistors forming a voltage divider to bias the plurality of anodes
Data Source
AI summary
Apparatus and methods for charge collection control in radiation detectors are provided. One radiation detector includes a semiconductor substrate, at least one cathode on a surface of the semiconductor substrate, and a plurality of anodes on a surface of the semiconductor substrate opposite the at least one cathode, wherein the plurality of anodes have gaps therebetween. The radiation detector further includes a charge collection control arrangement configured to cause one or more charges induced within the semiconductor substrate by incident photons to drift towards one or more of the plurality of anodes.