Radiation hardness of gallium nitride

Abstract

Gallium nitride (GaN) light emitting diodes (LEDs) were irradiated at room temperature with electrons in the range 300-1400 keV. A threshold energy of 440 keV was observed, corresponding to a gallium atom displacement energy of 19/spl plusmn/2 eV. This value of the displacement energy compares with that of silicon carbide but is smaller than that of diamond and larger than that of gallium arsenide (GaAs). No threshold energy for the nitrogen atom was observed. It is concluded that the nitrogen sublattice repairs itself through annealing. The measured displacement energy is used to determine the Rutherford cross section, which permits a theoretical comparison of electron and proton irradiation damage in GaN. The effects of 2.5 MeV electrons on gallium nitride films have been studied by photoluminescence (PL), and according to the literature, they introduce transitions in the near infrared part of the spectrum. Experiments on gallium nitride films using 2 MeV protons are reported in this work. The same transitions in the near infrared part of the spectrum are observed by PL. It is deduced that 2 MeV protons are about 1000 times more damaging than 2.5 MeV electrons. The Rutherford cross section predicts a value of 214. The difference is attributed to the defect recombination rate which depends on the particle type. The nature of the transitions in the near infrared part of the spectrum is reviewed. The GaN films were annealed at 400/spl deg/C for 30 min. As a result of annealing, another transition appears in the green part of the spectrum. Transitions involving the gallium vacancy in irradiated GaN are discussed.