Rutherford backscattering and nuclear reaction analyses of hydrogen ion-implanted ZnO bulk single crystals

The origins of low resistivity in H ion-implanted ZnO bulk single crystals are studied by Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA) photoluminescence (PL), and Van der Pauw methods. The H-ion implantation (peak concentration: 1.45 × 1020 cm−3) into ZnO is performed using a 500 keV implanter. The resistivity decreases from 2.5 × 103 Ω cm for unimplanted ZnO to 6.5 Ω cm for as-implanted one. RBS measurements show that Zn interstitial as a shallow donor is not recognized in as-implanted samples. From photoluminescence measurements, the broad green band emission is observed in as-implanted samples. NRA measurements for as-implanted ZnO suggest the existence of the oxygen interstitial. The origins of the low resistivity in the as-implanted sample are attributed to both the H interstitial as a shallow donor and complex donor between H and disordered O. The activation energy of H related donors estimated from the temperature dependence of carrier concentration is 29 meV.