Ion beam induced charge imaging of epitaxial GaN detectors

We report the use of ion beam induced charge imaging to characterise the charge signal uniformity of epitaxial gallium nitride radiation detectors. The detectors were fabricated from 2 μm thick semi-insulating gallium nitride, grown by MOCVD on a sapphire substrate. A carrier concentration of 1.4×1015 cm−3 was measured using capacitance–voltage measurements. Ion beam induced charge imaging was carried out with a 2 MeV alpha particle beam focussed to a 3 μm diameter and raster scanned across the device. The resulting ion beam images show excellent charge signal uniformity in this material with no evidence of material defects or polycrystalline structure on the micrometer length scale. No evidence of charge signal trapping was observed in these devices.