论文标题
通过共同掺杂和缺陷关联调整GAN中Europium和Luminence中心的价和浓度
Tuning the valence and concentration of europium and luminescence centers in GaN through co-doping and defect association
论文作者
论文摘要
使用第一原理杂交密度功能缺陷计算，研究了欧洲裔（EU）掺杂GAN的缺陷物理。这包括稀土掺杂剂与天然点缺陷（GA和N空缺）与其他杂质（O，Si，C，H和Mg）的相互作用，这是无意间存在或故意纳入宿主材料的。尽管在Wurtzite gan的GA站点合并欧盟时，通常发现三价欧盟$^{3+} $ ion主要是主要的，但二价eu $^{2+} $也是稳定的，并且在频段 - 频段范围的fermi-Level值中也是如此。 EU $^{2+} $/eu $^{3+} $比率可以通过调整费米级别的位置和缺陷关联来调节。我们发现与氧气共同掺杂可以促进将欧盟掺入晶格中。非相关的欧盟$ _ {\ rm ga} $是一个电动和光学活跃的缺陷中心，其行为受到局部缺陷 - 缺陷相互作用的深刻影响。缺陷复合物，例如eu $ _ {\ rm ga} $ - o $ _ {\ rm n} $，eu $ _ {\ rm ga} $ - si $ _ {\ rm ga} $，eu $ _ {\ rm ga} ga} $ - mg $ _ {\ rm ga} $，以及eu $ _ {\ rm ga} $ - o $ $ _ {\ rm n} $ - mg $ - mg $ _ {\ rm ga} $可以有效地充当深层的载波陷阱，然后从主机中介导eu $ $ $ $ $^$ $^$^$^$^$^$^$^$^$^$^4f;内部$ f $发光。与欧盟相关的缺陷也可能导致缺陷 - 波段发光。例如，未关联的欧盟$ _ {\ rm ga} $被确定为在n型中观察到的宽蓝色发射的可能来源，eu $^{2+} $ - 包含gan。这项工作要求对先前针对欧盟掺杂的GAN进行的特定缺陷配置进行某些假设进行重新评估，并进一步研究在（EU，MG）掺杂样品中观察到的光致发光磁滞的起源。
Defect physics of europium (Eu) doped GaN is investigated using first-principles hybrid density-functional defect calculations. This includes the interaction between the rare-earth dopant and native point defects (Ga and N vacancies) and other impurities (O, Si, C, H, and Mg) unintentionally present or intentionally incorporated into the host material. While the trivalent Eu$^{3+}$ ion is often found to be predominant when Eu is incorporated at the Ga site in wurtzite GaN, the divalent Eu$^{2+}$ is also stable and found to be predominant in a small range of Fermi-level values in the band-gap region. The Eu$^{2+}$/Eu$^{3+}$ ratio can be tuned by tuning the position of Fermi level and through defect association. We find co-doping with oxygen can facilitate the incorporation of Eu into the lattice. The unassociated Eu$_{\rm Ga}$ is an electrically and optically active defect center and its behavior is profoundly impacted by local defect--defect interaction. Defect complexes such as Eu$_{\rm Ga}$-O$_{\rm N}$, Eu$_{\rm Ga}$-Si$_{\rm Ga}$, Eu$_{\rm Ga}$-H$_i$, Eu$_{\rm Ga}$-Mg$_{\rm Ga}$, and Eu$_{\rm Ga}$-O$_{\rm N}$-Mg$_{\rm Ga}$ can efficiently act as deep carrier traps and mediate energy transfer from the host into the Eu$^{3+}$ $4f$-electron core which then leads to sharp red intra-$f$ luminescence. Eu-related defects can also give rise to defect-to-band luminescence. The unassociated Eu$_{\rm Ga}$, for example, is identified as a possible source of the broad blue emission observed in n-type, Eu$^{2+}$-containing GaN. This work calls for a re-assessment of certain assumptions regarding specific defect configurations previously made for Eu-doped GaN and further investigation into the origin of the photoluminescence hysteresis observed in (Eu,Mg)-doped samples.
