CdTe Semiconductor Radiation Converter Material for High-Flux X-Ray Detection
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Solution Overview
Problem
Radiation converter materials used in human-medical X-ray tomography face challenges in detecting high-flux X-ray quanta due to polarization effects from defect sites, leading to reduced spectral sensitivity and increased dark current, which compromises image quality and signal-to-noise ratio.
Innovation Solution
A semiconductor material with a specific dopant concentration and defect sites produced through a controlled process to achieve an ohmic resistivity range of 5·10^7 Ω·cm to 2·10^9 Ω·cm, optimizing the compromise between polarization and spectral sensitivity, using materials like CdTe or CdZnTe with dopants such as Cl or In, and heat treatment to set the defect site concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor material is heavily doped to minimize polarization effects, then the charge carrier lifetime is improved, but the ohmic resistivity decreases leading to high dark current
Solution Approach 1:
The patent applies parameter changes by precisely controlling the dopant concentration within a specific range (10^15 to 10^17 atoms/cm³) and managing defect site concentrations to achieve an optimal balance. This resolves the contradiction by finding a parameter window where sufficient doping reduces polarization effects while maintaining adequate ohmic resistivity to limit dark current to acceptable levels.
Solution Approach 2:
The patent implements local quality by creating specific defect sites (vacancies, interstitial atoms) in controlled concentrations alongside the dopant distribution. This localized structural modification allows different regions of the semiconductor material to have optimized properties: dopant atoms passivate harmful defect sites to extend charge carrier lifetime, while the controlled defect concentration maintains electrical resistance to suppress dark current.
2Measurement precision
If the dopant concentration is increased to passivate defect sites, then the spectral sensitivity is improved, but the ohmic resistivity decreases causing reduced signal-to-noise ratio
Solution Approach 1:
The patent resolves this contradiction through parameter changes by establishing a specific dopant concentration range (10^15 to 10^17 atoms/cm³) that provides sufficient defect site passivation to maintain spectral sensitivity while preventing excessive doping that would reduce ohmic resistivity and increase dark current noise. The controlled defect site concentration further optimizes this balance.
Solution Approach 2:
The patent employs composite material principles by combining dopant atoms with controlled defect sites (vacancies and interstitial atoms) within the semiconductor crystal structure. This composite approach creates a material with dual functionality: dopant atoms provide electrical properties and defect passivation for spectral sensitivity, while controlled defect concentrations maintain electrical resistance to suppress dark current and preserve signal-to-noise ratio.
3Speed
If the defect site concentration is reduced to minimize polarization effects, then the charge carrier mobility is improved, but the material becomes more susceptible to recombination losses
Solution Approach 1:
The patent applies local quality by creating specific defect sites (vacancies, interstitial atoms) in controlled concentrations alongside the dopant distribution. This localized structural modification allows different regions of the semiconductor material to have optimized properties: dopant atoms passivate harmful defect sites to extend charge carrier lifetime, while the controlled defect concentration maintains electrical resistance to suppress dark current.
Solution Approach 2:
The patent employs composite material principles by combining dopant atoms with controlled defect sites (vacancies and interstitial atoms) within the semiconductor crystal structure. This composite approach creates a material with dual functionality: dopant atoms provide electrical properties and defect passivation to extend charge carrier lifetime, while controlled defect concentrations prevent excessive recombination losses by providing controlled charge trapping sites.
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 approach enhances the signal-to-noise ratio and image quality in high-flux applications by maintaining a lower polarization and higher spectral sensitivity, allowing for efficient detection of X-ray quanta with improved temporal resolution and increased maximum detectable flux.
Implementation Method 1
directly converting radiation quanta into electrical charge carriers
Implementation Method 2
the material is doped with a dopant with the aim of minimizing the polarization effects. In this case, the doping atoms introduced are intended to passivate or compensate for the defect sites present in the crystal
Implementation Method 3
heat treatment to set the defect site concentration
Data Source
AI summary
A radiation converter material includes a semiconductor material used for directly converting radiation quanta into electrical charge carriers. In at least one embodiment, the semiconductor material includes a dopant in a dopant concentration and defect sites produced in a process-dictated manner in such a way that the semiconductor material includes an ohmic resistivity in a range of between 5·107 Ω·cm and 2·109 Ω·cm. Such a radiation converter material is particularly well matched to the requirements in particular in human-medical applications with regard to the high flux rate present and the spectral distribution of the radiation quanta. In at least one embodiment, the invention additionally relates to a radiation converter and a radiation detector, and a use of and a method for producing such a radiation converter material.