A New Radiation Hard Semiconductor — Semi‐Insulating GaN: Photoelectric Properties

The anticipated upgrade of the CERN Large Hadron Collider to ten times brighter luminosity poses a severe challenge to semiconductor detectors in the CERN experiments. The suitability of semi‐insulating GaN (SI‐GaN), proposed as an alternative to silicon for the fabrication of radiation hard detectors, is investigated here in MOCVD GaN layers grown on sapphire. The electrical properties of SI‐GaN were studied by dc and microwave techniques, and defect parameters determined by the method of thermally stimulated currents. Variations of charge collection efficiency (CCE) in SI‐GaN diodes induced by ionizing radiation of 5.48 MeV alpha particles were revealed. Samples were also irradiated by X‐rays, reactor neutrons and high‐energy proton fluences of up to 1016 cm−2. The high radiation hardness of SI‐GaN was demonstrated by the modest reduction in CCE, from 92% to 77%, in the material irradiated by neutrons (up to a fluence of 1015 cm−2). The CCE was unaffected by an X‐rays dose of 600 MRad), but decreased to a few % after proton and neutron fluences of 1016 cm−2. The electrical characteristics vary more significantly, depending on irradiation type and dose. Fast decay components and a significant role of percolation effects are observed in the photoconductivity transients.