论文标题
金红石geo $ _2 $和p-type掺杂的浅价带
Shallow Valence Band of Rutile GeO$_2$ and P-type Doping
论文作者
论文摘要
Geo $ _2 $具有$α$ -Quartz-type晶体结构，其基本带隙非常宽，为6.6 eV，是一个很好的绝缘体。在这里，我们发现具有4.6 eV频段差距的稳定的金黄色geo $ _2 $ polymorph具有出人意料的低$ \ sim $ 6.8 ev离子化潜力，如使用第一原则计算所预测的。由于金红石结构中的距离很短，其中包含小有效离子半径的阳离子，例如ge $^{4+} $，因此O 2P轨道之间的抗dy抗相互作用会提高价带的最大能级，从而使孔掺杂似乎可行。在实验上，我们报告了$ 1.5 \ times 1.0 \ times 0.8 $ mm $^3 $大的金红石geo $ _2 $单晶的通量增长，并确认温度的热稳定性高达$ 1021 \ pm 10〜^\ circc $ c。 X射线荧光光谱表明，Li $ _2 $ o $ $ $ $ $ $ $ _3 $ flux中包含了无意的MO杂质，以及GA在R-Geo $ _2 $ lattice中的溶解度作为潜在的受体剂。 Ga-和Mo编码的R-Geo $ _2 $单晶的电阻在室温下很高，但加热后降低2-3个数量级，至300 $^\ Circ $ C，这归因于热激活的P型传导。
GeO$_2$ has an $α$-quartz-type crystal structure with a very wide fundamental band gap of 6.6 eV and is a good insulator. Here we find that the stable rutile-GeO$_2$ polymorph with a 4.6 eV band gap has a surprisingly low $\sim$6.8 eV ionization potential, as predicted from the band alignment using first-principles calculations. Because of the short O$-$O distances in the rutile structure containing cations of small effective ionic radii such as Ge$^{4+}$, the antibonding interaction between O 2p orbitals raises the valence band maximum energy level to an extent that hole doping appears feasible. Experimentally, we report the flux growth of $1.5 \times 1.0 \times 0.8$ mm$^3$ large rutile GeO$_2$ single crystals and confirm the thermal stability for temperatures up to $1021 \pm 10~^\circ$C. X-ray fluorescence spectroscopy shows the inclusion of unintentional Mo impurities from the Li$_2$O$-$MoO$_3$ flux, as well as the solubility of Ga in the r-GeO$_2$ lattice as a prospective acceptor dopant. The resistance of the Ga- and Mo-codoped r-GeO$_2$ single crystals is very high at room temperature, but it decreases by 2-3 orders of magnitude upon heating to 300 $^\circ$C, which is attributed to thermally-activated p-type conduction.
