Lattice disorder in neutron irradiated GaN: Nuclear reaction analysis and Rutherford backscattering studies

Disorders of N and Ga lattice in GaN, introduced by fast neutron irradiation with a fluence of 6.7 × 1018 cm−2, are investigated by nuclear reaction analysis (NRA) using 14N(d, p)15N reaction with 2.6 MeV D2+ ions and by Rutherford backscattering (RBS) with 1.5 MeV 4He+ ions. The 〈0 0 0 1〉 aligned NRA yield measured in as-irradiated GaN slightly increases compared with that of un-irradiated crystals, indicating that primary knock-on (PKO) produced by the neutrons results in ∼7.2 × 102 displaced N atoms. The slight increase in the aligned RBS yield for as-irradiated samples relative to that of un-irradiated ones indicates that the ∼1.8 × 102 displaced Ga atoms are produced by PKO. The displacement of N atoms is four times larger than that of Ga atoms, reflecting the lighter weight of N than Ga, although both the displacements are recovered by annealing over 1000 °C. The displacement of Ga atoms in GaN is two times smaller than that in GaP (∼3.0 × 102 atoms/PKO), showing the stronger bonds in GaN than GaP.