发表机构
University of South Carolina; University of California, Santa Barbara（南卡罗来纳大学; 加州大学圣塔芭芭拉分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过第一性原理计算，明确了单斜相和刚玉相Ga₂O₃与Al₂O₃中F、Cl作为施主的特性，发现Cl是(AlₓGa₁₋ₓ)₂O₃及纯Al₂O₃中极具潜力的施主候选体。
AI 中文摘要
我们对Ga₂O₃和Al₂O₃中的卤族杂质（F和Cl）开展了系统的第一性原理研究，同时考虑了单斜相和刚玉相两种晶型。我们针对结构性质、形成能以及电荷态转变能级的研究，明确了不同原子构型和电荷态的相对稳定性。研究发现，在单斜相和刚玉相Ga₂O₃中，占据氧位点的F和Cl均表现为浅施主。然而，随着Al组分增加导致带隙增大，二者的行为出现显著差异：F易形成DX中心，在单斜相(AlₓGa₁₋ₓ)₂O₃中Al浓度达38%时发生自补偿，在刚玉相(AlₓGa₁₋ₓ)₂O₃中则在Al浓度达70%时发生自补偿；而Cl更不易形成DX中心，在单斜相(AlₓGa₁₋ₓ)₂O₃中，占据最低能量氧位点的Cl_O在合金组分达50%时才开始出现DX行为，在刚玉相(AlₓGa₁₋ₓ)₂O₃中，Cl_O的DX行为起始仅发生在Al浓度高达84%时。我们还研究了间隙态的F和Cl，发现它们可作为补偿中心，但迁移势垒足够低，可通过生长后退火去除。值得注意的是，在单斜相和刚玉相Al₂O₃中，Cl_O的电荷态转变能级约为导带底下方0.48 eV，比F_O及其他施主候选体的能级浅得多。这些结果表明，Cl是(AlₓGa₁₋ₓ)₂O₃合金乃至纯Al₂O₃中极具潜力的施主候选体，不过较高的形成能和补偿效应将导致纯Al₂O₃中难以观测到本征n型导电性。
英文摘要
We present a systematic first-principles investigation of halide impurities (F and Cl) in Ga$_2$O$_3$ and Al$_2$O$_3$, considering both monoclinic and corundum phases. Our study of the structural properties, formation energies, and charge-state transition levels establishes the relative stability of different atomic configurations and charge states. We find that F and Cl on oxygen sites act as shallow donors in Ga$_2$O$_3$ in both the monoclinic and corundum phases. However, their behavior differs substantially as the band gap increases with greater Al compositions. Fluorine is prone to $DX$-center formation with increased Al composition, leading to self-compensation at 38% Al concentration in monoclinic (Al$_x$Ga$_{1-x}$)$_2$O$_3$ and 70% Al concentration in corundum (Al$_x$Ga$_{1-x}$)$_2$O$_3$. Chlorine is more resistant to $DX$-center formation: in monoclinic (Al$_x$Ga$_{1-x}$)$_2$O$_3$, Cl$_\mathrm{O}$ on the lowest-energy oxygen site shows an onset of $DX$ behavior at 50% alloy composition, while in corundum (Al$_x$Ga$_{1-x}$)$_2$O$_3$ this onset for Cl$_\mathrm{O}$ occurs only at Al concentrations as high as 84%. We also study F and Cl interstitials, finding that they act as compensating centers but also exhibit migration barriers that are low enough for them to be removed by post-growth annealing. Surprisingly, in both monoclinic and corundum Al$_2$O$_3$, Cl$_\mathrm{O}$ exhibits a relatively shallow transition level located at $\sim$0.48 eV below the conduction-band minimum, much shallower than F$_\mathrm{O}$ and other donor candidates. These remarkable results identify Cl as an unusually promising donor candidate in (Al$_x$Ga$_{1-x}$)$_2$O$_3$ alloys and even pure Al$_2$O$_3$, although high formation energies and compensation will render observation of true $n$-type conductivity in Al$_2$O$_3$ difficult.
Comments13 pages, 6 figures
