562015-03-24 , 法政大学大学院理工学・工学研究科
Neutron transmutation doped(NTD)-GaN, which is irradiated with fast and thermal neutrons at fluxes of 6.7 x 1018 cm-2 and 1.4 x 1019 cm-2, respectively, keeps the high resistivity of 108 Ωcm at room temperature. The energy level estimated from the temperature dependence of carrier concentration by high temperature alternating current Hall effect measurements is 960 meV. This energy is attributed to the nitrogen interstitial (Ni) as a deep acceptor level located below the bottom of the conduction band, whose level is close to that of the nitrogen split interstitial. In Rutherford backscattering spectroscopy/channeling measurements using 1.5 MeV H+ ions, the lattice displacement of N atoms is observed, suggesting the existence of Ni. Neutron-transmuted DX-like center of Ge as a donor is compensated by both Ni and 14C acceptors generated from the (n,p) reaction of 14N. The origins of high resistivity after the neutron irradiation are attributed to these acceptors.