Abstract The anisotropic optical constants of high-quality, single crystalline Ga2O3 films in both orthorhombic (e) and monoclinic (β) phases were obtained from ellipsometry study. The (0001)-oriented e-Ga2O3 and a (−201) β-Ga2O3 epilayers were grown on (0001) α-Al2O3 substrates by mist-chemical vapor deposition and pulsed laser deposition, respectively. The experimental bandgaps derived from optical constants were found to be related with the allowed optical transitions from valence sub-bands to conduction band minimum in terms of the polarization-selection rules in such asymmetric structures. The pseudo-ordinary (a-b plane) and extraordinary (c axis) optical bandgaps of the e-Ga2O3 film were estimated to be 4.85 ± 0.02 and 4.76 ± 0.02 eV, respectively. The pseudo ordinary (b axis) and extraordinary (a-c plane) optical bandgaps of the β-Ga2O3 film were estimated to be 4.92 ± 0.02 and 4.57 ± 0.02 eV, respectively. The energy difference between the two bandgaps of the e-Ga2O3 is about 0.09 eV, which matches the theoretically calculated energy difference (about 0.06 eV) of the highest two valence bands.

中文翻译：

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正交和单斜相单相 Ga2O3 薄膜各向异性光学常数的椭偏测定

摘要 通过椭偏仪研究获得了正交(e) 和单斜(β) 相的高质量单晶Ga2O3 薄膜的各向异性光学常数。(0001) 取向的 e-Ga2O3 和 (-201) β-Ga2O3 外延层分别通过雾化学气相沉积和脉冲激光沉积在 (0001) α-Al2O3 衬底上生长。根据这种不对称结构中的偏振选择规则，发现从光学常数导出的实验带隙与从价子带到导带最小值的允许光学跃迁有关。e-Ga2O3 薄膜的伪普通（ab 平面）和异常（c 轴）光学带隙估计分别为 4.85 ± 0.02 和 4.76 ± 0.02 eV。β-Ga2O3 薄膜的伪普通（b 轴）和异常（ac 平面）光学带隙估计分别为 4.92 ± 0.02 和 4.57 ± 0.02 eV。e-Ga2O3 的两个带隙之间的能量差约为 0.09 eV，与理论计算的最高两个价带的能量差（约 0.06 eV）相匹配。