(Cd,Mg)Te crystals for picosecond-response optical-to-x-ray radiation detectors

Area of Science:

• Materials Science
• Optoelectronics
• X-ray Physics

Background:

• Developing sensitive photodetectors is crucial for advanced spectroscopy.
• Existing detectors often lack sensitivity to both optical and X-ray wavelengths.
• Ultrafast pump-probe spectroscopy requires precise timing capabilities.

Purpose of the Study:

• To demonstrate a novel photodetector sensitive to both optical and X-ray picosecond pulses.
• To characterize the performance of a new Indium-doped Cadmium Magnesium Telluride (Cd,Mg)Te single crystal photodetector.
• To assess the suitability of the photodetector for free-electron laser (FEL) applications.

Main Methods:

• Grown In-doped Cd$_{0.96}$Mg$_{0.04}$Te single crystal material.
• Fabricated a photodetector based on the grown crystal.
• Measured femtosecond optical photoresponse and detector performance (dark current, responsivity).
• Exposed the detector to Ti Kα X-ray pulses generated by a free-electron laser and measured photoresponse.

Main Results:

• Achieved <100-pA dark current and 0.22-mA/W responsivity at 780-nm optical wavelength.
• Observed a 200-ps full-width-at-half-maximum photoresponse to 4.5 keV X-ray pulses.
• Demonstrated suitability for coarse timing in X-ray/optical pump-probe spectroscopy.

Conclusions:

• The developed (Cd,Mg)Te photodetector exhibits excellent performance for both optical and X-ray detection.
• The detector's fast response time makes it valuable for ultrafast spectroscopy.
• This material offers a promising solution for timing applications in free-electron laser experiments.