Co-doped CdZnTe Semiconductor Materials for Radiation Detectors
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Solution Overview
Problem
High-purity intrinsic CdZnTe compounds used in radiation detectors exhibit low electrical resistivity and inadequate charge transport properties due to intrinsic defects and impurities, preventing full depletion and leading to variable performance across growths.
Innovation Solution
The use of co-doping or triple doping with specific elements from Group III and VII, along with rare earth metals like Erbium, to control and compensate for intrinsic defects, achieving full depletion and improved resistivity in CdZnTe semiconductor materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-purity intrinsic CdZnTe compounds are used, then material purity is improved, but electrical resistivity decreases and charge transport properties deteriorate
Solution Approach 1:
The patent applies parameter changes by introducing controlled doping elements (Group III elements like Al, Ga, In and Group VII elements like Cl, Br, I) at specific concentrations to modify the electrical properties of CdZnTe. This transforms the material from intrinsic to extrinsic semiconductor, achieving high electrical resistivity (greater than 10^9 ohm-cm) while maintaining structural integrity and purity.
Solution Approach 2:
The patent creates a composite doped semiconductor structure by combining CdZnTe base material with multiple dopant elements. The co-doping or tri-doping scheme integrates different elements that work synergistically: Group III elements provide hole carriers, Group VII elements provide electron carriers, and rare earth elements passivate defects, resulting in a composite material with superior electrical resistivity and charge transport properties.
2Ease of manufacture
If intrinsic defects are present in CdZnTe, then material formation is simplified, but full depletion capability is lost
Solution Approach 1:
The patent converts harmful intrinsic defects into beneficial effects by using rare earth element dopants (such as Er, Eu, Gd) that preferentially bind to and passivate defect sites. The dopants transform the detrimental impact of vacancies and antisites into controlled electrical properties, enabling full depletion while maintaining the simplicity of crystal growth processes.
Solution Approach 2:
Rare earth element dopants act as intermediaries between intrinsic defects and the electrical properties of CdZnTe. These dopants mediate the interaction by binding to defects and modifying their electrical activity, thereby enabling full depletion capability without requiring complete elimination of intrinsic defects or complex growth procedures.
3Ease of manufacture
If impurities and native defects are incorporated uncontrolled, then growth process is simplified, but carrier transport properties deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling dopant concentrations and ratios during crystal growth. By maintaining specific doping levels (e.g., 10^15 to 10^18 atoms/cm³ for rare earth elements) and optimizing the combination of dopants, the method achieves excellent carrier transport properties (electron mobility × lifetime greater than 10^-³ cm²/V) while keeping the growth process relatively simple and scalable.
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 compensation scheme enhances charge transport properties, reduces spatial variations, and enables full depletion, resulting in improved performance and accuracy for radiation detection applications, particularly in gamma and X-ray imaging.
Implementation Method 1
The use of co-doping or triple doping with specific elements from Group III and VII, along with rare earth metals like Erbium, to control and compensate for intrinsic defects, achieving full depletion and improved resistivity in CdZnTe semiconductor materials
Data Source
AI summary
Semiconductor materials suitable for being used in radiation detectors are disclosed. A particular example of the semiconductor materials includes tellurium, cadmium, and zinc. Tellurium is in molar excess of cadmium and zinc. The example also includes aluminum having a concentration of about 10 to about 20,000 atomic parts per billion and erbium having a concentration of at least 10,000 atomic parts per billion.