Evolution of high-dose implanted hydrogen in ZnO

We have investigated evolution of implanted H in single crystalline ZnO in the temperature range from room temperature (RT) to 600 ∘C. H was implanted at RT with an energy of 100 keV and a dose of 2×1017 cm−2. Secondary Ion Mass Spectrometry (SIMS) was used for the study of H distribution. The effect of the implanted H on electrical properties of ZnO as a function of depth was investigated by Scanning Spreading Resistance Microscopy (SSRM) and Scanning Capacitance Microscopy (SCM). After the implantation, the SIMS measurements reveal a H profile with a peak concentration of ∼1022 cm−3 at a depth of 0.7 μm. An increased carrier concentration is observed by SSRM and SCM in the as-implanted sample in the H implanted region. After heat treatment for 2 h at 200 ∘C, no change in either H or carrier concentration profiles is detected. Annealing for 2 h at 400 ∘C leads to a decrease in the peak H concentration down to 2×1021 cm−3. However, no diffusion-like broadening of the H profile is revealed. Heat treatment at 600 ∘C results in a further decrease of the H concentration to 2×1020 cm−3 and, similarly to the 400 ∘C annealing, no broadening of the H profile is observed. This suggests that the implanted H is trapped in immobile complexes which dissociate during annealing with subsequent out-diffusion of H from the implanted region. The correlation between electrical activity of H and presence of radiation damage is discussed.