GaN detector development for particle and X-ray detection

We report on preliminary alpha particle and X-ray measurements on a number of prototype GaN PIN diodes. The aim of the study was to investigate the potential use of GAN based radiation detectors for radiation hard, high temperature, solar blind space applications. The devices have a planar structure consisting of a 2 μm epitaxial GaN layer grown on a highly doped n-type AlxGa1−xN nucleation layer, which in turn is deposited on a p-type 4H–SiC substrate. Au ohmic contacts were applied to the top of the GaN layer and the bottom of the substrate. A number of different sized devices were tested with contact diameters ranging from 0.4 mm to 0.7 mm. All devices showed good diode behaviour with reverse leakage currents in the tens to hundreds of micro-amp range. C–V measurements showed that the GaN layers were fully depleted for biases >20 V. When exposed to a 5.5 MeV alpha particle source, the devices showed a spectroscopic response with energy resolutions of ∼25% FWHM at room temperature (RT) and 10 V bias and 20% FWHM at −50 °C. These values are consistent with the previous measurements. No response to 60 keV photons could be measured.