Self-Diffusion in beta-Ga2O3 Single Crystals

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Gallium oxide (beta-Ga2O3) is an ultra-wide bandgap semiconductor with increasing importance in various technological fields because of its multifunctional use in diverse applications (power electronics, gas sensor, photo detector, transparent conducting oxide etc.). The electrical and optical properties of beta-Ga2O3 depend critically on the concentration, charge state and migration of native point defects (oxygen vacancies, gallium interstitials, gallium vacancies etc.). Self-diffusion experiments can give information on the nature of native defects and their mobility in the material. However, up to now there are no self-diffusion studies available in literature.The aim of the present proposal is the systematic experimental determination of oxygen and gallium tracer diffusivities in beta-Ga2O3 single crystals as a function of temperature. This work will be carried out with secondary ion mass spectrometry (SIMS). Oxygen tracer diffusion experiments will be achieved by isotope exchange using 18O2 as a gaseous tracer source. In order to investigate the Ga diffusion, Al will be used as a substitute tracer. From the results, activation energies and pre-exponential factors will be derived. The diffusion experiments will be done as a function of oxygen partial pressure at different temperatures. By consideration of fundamental defect reactions and comparison to theoretical work as given in literature, certain model assumptions on dominating defect structures and their kinetics can be proven or discarded. The results will also help to understand the oxygen partial pressure dependence of electronic conductivity and the contribution of ion conductivity at moderate temperatures below 900 K.