Self-Diffusion in beta-Ga2O3 Single Crystals

氧化镓(β-Ga_2O_3)是一种超宽带隙半导体，由于其在电力电子、气体传感器、光电探测器、透明导电氧化物等领域的多功能应用，在各个技术领域具有越来越重要的作用。β-Ga_2O_3的电学和光学性质与本征点缺陷(氧空位、镓间隙、镓空位等)的浓度、电荷状态和迁移密切相关。自扩散实验可以提供有关本征缺陷的性质及其在材料中的迁移率的信息。然而，到目前为止，还没有文献中关于自扩散的研究，本方案的目的是系统地实验测定β-Ga2O_3单晶中氧和镓的示踪扩散系数随温度的变化。这项工作将使用二次离子质谱仪(SIMS)进行。氧示踪扩散实验将通过使用18O2作为气态示踪源的同位素交换来实现。为了研究Ga的扩散，将使用Al作为替代示踪剂。从计算结果中可以得到活化能和指前因子。扩散实验将在不同温度下作为氧分压的函数进行。通过考虑基本的缺陷反应，并与文献中给出的理论工作进行比较，可以证明或放弃关于主导缺陷结构及其动力学的某些模型假设。这些结果也有助于理解电子电导率与氧分压的关系，以及在900K以下的中温离子电导率的贡献。

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.