Implant isolation of ZnO

We study ion-irradiation-induced electrical isolation in n-type single-crystal ZnO epilayers. Emphasis is given to improving the thermal stability of isolation and obtaining a better understanding of the isolation mechanism. Results show that an increase in the dose of 2 MeV ${}^{\mathrm{16}}\mathrm{O}$ ions (up to $\text{∼2}$ orders of magnitude above the threshold isolation dose) and irradiation temperature (up to $\text{350\hspace{0.05em}°}\mathrm{C})$ has a relatively minor effect on the thermal stability of electrical isolation, which is limited to temperatures of $\text{∼300–400\hspace{0.05em}°}\mathrm{C}.$ An analysis of the temperature dependence of sheet resistance suggests that effective levels associated with irradiation-produced defects are rather shallow $\text{(<50\hspace{0.17em}}\mathrm{meV}\mathrm{).}$ For the case of implantation with keV Cr, Fe, or Ni ions, the evolution of sheet resistance with annealing temperature is consistent with defect-induced isolation, with a relatively minor effect of Cr, Fe, or Ni impurities on the thermal stability of isolation. Results also reveal a negligible ion-beam flux effect in the case of irradiation with 2 MeV ${}^{\mathrm{16}}\mathrm{O}$ ions, supporting high diffusivity of ion-beam-generated defects during ion irradiation and a very fast stabilization of collision cascade processes in ZnO. Based on these results, the mechanism for electrical isolation in ZnO by ion bombardment is discussed.