**4. Conclusions**

The present study reports an experimental quantitative characterisation of radiationinduced vacancies in GaAs obtained in proton irradiation experiments using a wide range of proton fluxes. The experimental data were obtained by positron annihilation lifetime spectroscopy, considering the actual stopping profiles of both projectile (proton) and probe (positron) particles. The present research can be summarised as follows:


In the next experiment, these conclusions will be used for proposing irradiation studies on other types of semiconductors, including wide bandgap semiconductors. A planned combination of PAS experiments and measurements of the electrical properties of the irradiated materials, such as resistivity and free charge carriers' concentration, will

potentially increase the knowledge about the radiation tolerance of WBG materials, which are inevitable in numerous applications, including space exploration and safety for nuclear power installations.

**Author Contributions:** Conceptualization, I.N. and V.K.; methodology, I.N., V.K. and P.N.; irradiation experiment P.N.; software, M.P.; investigation, M.P. and S.S.; data curation, I.N. and V.K.; writing— original draft preparation, I.N. and V.K.; writing—review and editing, V.S., P.N. and J.D.; supervision, V.K.; project administration, V.K, J.D., P.N. and V.S.; funding acquisition, P.N. and V.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors would like to acknowledge partial support from the Slovak Research and Development Agency grants No. APVV-20-0010, APVV-20-0220 as well as from the European Regional Development Fund, projects No. ITMS2014+: 313011BUH7 and ITMS2014+: 313011W085. The authors further acknowledge financial contributions from the Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic and the Slovak Academy of Sciences, gran<sup>t</sup> number VEGA 1/0395/20.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data used to reach the conclusions are presented in the paper. Raw data and experimental logs are available upon request.

**Conflicts of Interest:** The authors declare no conflict of interest.
