标题： 铬杂质在$β$-Ga$_2$O$_3$中的表征 显示英文标题

标题： Characterization of Chromium Impurities in $β$-Ga$_2$O$_3$

摘要： 铬是一种常见的过渡金属杂质，在晶体生长过程中很容易被掺入。它或许最广为人知的是在掺铬的氧化铝（Al$_2$O$_3$）中激发了694.3纳米（1.786电子伏特）的发射，这一特性被用于红宝石激光器。此外，铬还被发现在单斜晶系氧化镓中，这是一种被研究用于功率电子学的宽禁带半导体。在这项工作中，我们通过理论和实验技术全面表征了铬在氧化镓（Ga$_2$O$_3$）中的行为。采用浮区法生长的$\beta$-Ga$_2$O$_3$样品显示出尖锐的光致发光信号，类似于红宝石。我们从头计算了铬形成的能量学，证明铬倾向于以中性杂质的形式占据八面体位置。铬具有四重基态自旋，并且在接近1.8电子伏特处有一个零声子线的内部跃迁。通过比较计算和实验测量的发光线型函数，我们阐明了与声子耦合的作用，并揭示了超出弗兰克-康登近似之外的特征。 强发射与小 Huang-Rhys 因子（0.05）以及具有技术相关性的宿主材料相结合，使得 Cr 在 Ga$_2$O$_3$中成为一种有吸引力的量子缺陷。 显示英文摘要

摘要： Chromium is a common transition-metal impurity that is easily incorporated during crystal growth. It is perhaps best known for giving rise to the 694.3 nm (1.786 eV) emission in Cr-doped Al$_2$O$_3$, exploited in ruby lasers. Chromium has also been found in monoclinic gallium oxide, a wide-bandgap semiconductor being pursued for power electronics. In this work, we thoroughly characterize the behavior of Cr in Ga$_2$O$_3$ through theoretical and experimental techniques. $\beta$-Ga$_2$O$_3$ samples are grown with the floating zone method and show evidence of a sharp photoluminescence signal, reminiscent of ruby. We calculate the energetics of formation of Cr from first principles, demonstrating that Cr preferentially incorporates as a neutral impurity on the octahedral site. Cr possesses a quartet ground-state spin and has an internal transition with a zero-phonon line near 1.8 eV. By comparing the calculated and experimentally measured luminescence lineshape function, we elucidate the role of coupling to phonons and uncover features beyond the Franck-Condon approximation. The combination of strong emission with a small Huang-Rhys factor of 0.05 and a technologically relevant host material render Cr in Ga$_2$O$_3$ attractive as a quantum defect.