Zinc gallate spinel dielectric function, band-to-band transitions, and Γ-point effective mass parameters
Zinc gallate spinel dielectric function, band-to-band transitions, and Γ-point effective mass parameters
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DOI：
10.1063/5.0043686
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发表时间：
2021-03
影响因子：
4
通讯作者：
M. Hilfiker;M. Stokey;R. Korlacki;U. Kılıç;Z. Galazka;K. Irmscher;S. Zollner;M. Schubert
中科院分区：
文献类型：
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作者：
M. Hilfiker;M. Stokey;R. Korlacki;U. Kılıç;Z. Galazka;K. Irmscher;S. Zollner;M. Schubert
我们确定新兴的超宽带隙半导体ZnGa 2 O 4的介电函数从近红外（0.75 eV）到真空紫外（8.5 eV）光谱区使用光谱椭圆偏振高品质的单晶基板。我们进行了密度泛函理论计算，并讨论了能带结构和布里渊区的Γ-点带-带跃迁能，它们的跃迁矩阵元和有效带质量参数。我们发现在Γ-点导带底部有一个各向同性的有效质量参数（0.24 me），它等于高度各向异性和简并价带顶部的最低价带有效质量参数（0.24 me）。我们计算的能带结构表明，尖晶石ZnGa 2 O 4是间接的，与最低的直接跃迁在Γ-点。我们分析了测量的介电函数使用临界点线形函数的三维，M0型货车霍韦奇异性，我们确定的直接带隙的能量为5.27（3）eV。在我们的模型中，我们还考虑了Wannier-Mott型激子的贡献，其有效Rydberg能量为14.8 meV。我们用外推法确定了近红外折射率（1.91），与最近的红外椭偏测量结果（e ∞ = 1.94）非常一致[M. Stokey，Appl. Phys. Lett. 117，052104（2020）]。
We determine the dielectric function of the emerging ultrawide bandgap semiconductor ZnGa2O4 from the near-infrared (0.75 eV) into the vacuum ultraviolet (8.5 eV) spectral regions using spectroscopic ellipsometry on high quality single crystal substrates. We perform density functional theory calculations and discuss the band structure and the Brillouin zone Γ-point band-to-band transition energies, their transition matrix elements, and effective band mass parameters. We find an isotropic effective mass parameter (0.24 me) at the bottom of the Γ-point conduction band, which equals the lowest valence band effective mass parameter at the top of the highly anisotropic and degenerate valence band (0.24 me). Our calculated band structure indicates the spinel ZnGa2O4 is indirect, with the lowest direct transition at the Γ-point. We analyze the measured dielectric function using critical-point line shape functions for a three-dimensional, M0-type van Hove singularity, and we determine the direct bandgap with an energy of 5.27(3) eV. In our model, we also consider contributions from Wannier–Mott type excitons with an effective Rydberg energy of 14.8 meV. We determine the near-infrared index of refraction from extrapolation (1.91) in very good agreement with results from recent infrared ellipsometry measurements ( e ∞ = 1.94) [M. Stokey, Appl. Phys. Lett. 117, 052104 (2020)].