β-Ga2O3 is a transparent conducting oxide that, due to its large bandgap of 4.8 eV, exhibits transparency into the UV. However, the free carriers that enable the conductivity can absorb light. We study the effect of free carriers on the properties of Ga2O3 using hybrid density functional theory. The presence of free carriers leads to sub-band-gap absorption and a Burstein-Moss shift in the onset of absorption. We find that for a concentration of 1020 carriers, the Fermi level is located 0.23 eV above the conduction-band minimum. This leads to an increase in the electron effective mass from 0.27–0.28 me to 0.35–0.37 me and a sub-band-gap absorption band with a peak value of 0.6 × 103 cm–1 at 3.37 eV for light polarized along the x or z direction. Both across-the-gap and free-carrier absorption depend strongly on the polarization of the incoming light. We also provide parametrizations of the conduction-band shape and the effective mass as a function of the Fermi level.

中文翻译：

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Ga2O3 中的子带隙吸收

β-Ga2O3 是一种透明的导电氧化物，由于其 4.8 eV 的大带隙，对紫外线具有透明性。然而，实现导电性的自由载流子可以吸收光。我们使用混合密度泛函理论研究了自由载流子对 Ga2O3 性质的影响。自由载流子的存在导致子带隙吸收和吸收开始时的 Burstein-Moss 位移。我们发现，对于 1020 个载流子的浓度，费米能级位于导带最小值上方 0.23 eV。这导致电子有效质量从 0.27–0.28 me 增加到 0.35–0.37 me，并且对于沿 x 或z 方向。跨隙吸收和自由载流子吸收都强烈依赖于入射光的偏振。我们还提供了作为费米能级函数的导带形状和有效质量的参数化。