GaAs x-ray detectors with sub-nanosecond temporal response

Area of Science:

• Materials Science
• Semiconductor Physics
• Radiation Detection

Background:

• Fast semiconductor radiation detectors are crucial for diagnostics in pulsed power applications.
• Silicon (Si) detectors are widely used but have limited hard X-ray absorption above 10 keV.
• Higher atomic number materials offer potential for improved X-ray absorption.

Purpose of the Study:

• To develop and evaluate Gallium Arsenide (GaAs) photodiodes as an alternative to Silicon (Si) detectors for hard X-ray detection.
• To assess the hard X-ray absorption efficiency and temporal response of GaAs detectors.
• To leverage the higher atomic number of GaAs for enhanced radiation detection capabilities.

Main Methods:

• Epitaxial growth of GaAs material at Sandia National Laboratories.
• Fabrication of GaAs photodiodes at Sandia's microfabrication facility.
• Characterization of detector performance, including hard X-ray absorption and temporal impulse response.

Main Results:

• GaAs photodiodes demonstrated over 10x higher hard X-ray absorption at 15 keV compared to similarly sized Si detectors.
• The temporal impulse response of the GaAs detectors was nearly identical to Si detectors, with a 0.5 ns full-width half maximum.
• Successful fabrication of GaAs detectors utilizing Sandia's advanced facilities.

Conclusions:

• GaAs photodiodes present a significant advancement for hard X-ray detection in pulsed power applications.
• The enhanced absorption of GaAs detectors, coupled with fast response times, offers improved diagnostic capabilities.
• GaAs detectors are a viable and superior alternative to Si detectors for high-energy X-ray measurements.