Development of Antimonide-based Energy-sensitive Radiation Detectors

摘要

This dissertation is devoted to studying radiation response of the antimonide (Sb)-based detectors and investigating the energy-resolving capability of the integrated GaSb/AlAsSb device structures for X-ray and gamma-ray spectrometry. Energy-sensitive radiation detectors have been extensively employed in applications including material characterization, biomedical research, and homeland security. The unique properties of Sb-based materials could enable an increased flexibility in using the technology for versatile applications. This work attempts to take advantage of Sb-based materials and utilize the heterostructure device concept to achieve this type of radiation detectors. The device development begins with investigating the radiation response of GaSb PIN device, and the energy-sensitive detection has been demonstrated for the first time. With a measurement temperature of 140 K, the device exhibits a full-width-at-half-maximum (FWHM) of 1.238 keV and 1.789 keV at 5.9 keV and 59.5 keV, respectively. The obtained energy resolution has been studied in detail to provide feedback on device design consideration. The heterostructure device architecture has been first approached with the GaSb/GaAs material system using the interfacial misfit (IMF) technique. While the devices show a low dark current floor at room-temperature, the potential barrier induced by the interface charges at the IMF arrays has prevented the effective collection of the carrier generated in the GaSb absorber. The lattice-matched AlAsSb alloy is then investigated as an alternative candidate to replace GaAs for the large-bandgap junction region. Digital-alloy growth of AlAsSb has been developed and gives enhanced optical and electrical characteristics in comparison to the traditional random-alloy growth. Finally, the heterostructure device for energy-sensitive radiation detection has been realized by integrating the GaSb absorber and the AlAsSb digital-alloy combined with a field-control layer to optimize the electric field profile. Well-defined X-ray and gamma-ray photopeaks are successfully obtained by the GaSb/AlAsSb devices under exposure to 241Am radioactive sources. The spectroscopic characterization shows improvement in the extracted excess noise component in comparison to the PIN structure by effectively eliminating the high peak electric field and surface recombination. The minimum FWHM of 1.283 keV at 59.5 keV has been achieved, and measured energy resolution is limited by the noise from the readout electronics rather than the detector material.