We report on the study of optical properties of mist CVD grown $\alpha $ -Ga₂O₃ with the observation of excitonic absorption in spectral responsivity measurements. 163 nm of Ga₂O₃ was grown on sapphire using Ga-(acac)₃ as the starting solution at a substrate temperature of 450°C. The film was found to be crystalline and of $\alpha $ -phase with an on-axis full width at half maximum (FWHM) of 92 arcsec as confirmed from X-ray diffraction scans. The Eliott-Toyozawa model was used to deduce band gap and excitonic binding energy from the absorption spectrum. The exciton binding energy was extracted to be 90 meV with large Gaussian spread of 0.195 eV. From spectral responsivity (S.R) measurements, a similar value of excitonic binding energy was found. This unusually huge binding energy is attributed to strong interaction between longitudinal optical (LO) phonons and excitons. Further, metal-semiconductor-metal (MSM) photodetectors (PD) with lateral inter-digitated geometry were fabricated on the film. A sharp band edge was observed at 229 nm (~ 5.42 eV) in the spectral response with peak responsivity of ~1 A/W at a bias of 20 V. The UV to visible rejection ratio was found to be ~ 100 while the dark current was measured to be ~ 0.1 nA at a bias voltage of 20 V.

中文翻译：

---

雾状 CVD 生长的 α-Ga2O3 的光学特性

我们报告了雾状 CVD 生长的光学特性的研究 $\alpha $ -Ga ₂ O ₃在光谱响应度测量中观察到激子吸收。在450℃的衬底温度下使用Ga-(acac) ₃作为起始溶液在蓝宝石上生长163nm的Ga ₂ O ₃。发现薄膜是结晶的，并且 $\alpha $ 从 X 射线衍射扫描证实，具有 92 弧秒的轴上半高全宽 (FWHM) 的 - 相位。Eliott-Toyozawa 模型用于从吸收光谱中推导出带隙和激子结合能。提取的激子结合能为 90 meV，高斯扩展为 0.195 eV。从光谱响应度 (SR) 测量中，发现了类似的激子结合能值。这种异常巨大的结合能归因于纵向光学 (LO) 声子和激子之间的强相互作用。此外，在薄膜上制造了具有横向交叉几何形状的金属-半导体-金属（MSM）光电探测器（PD）。在光谱响应中在 229 nm (~ 5.42 eV) 处观察到一个尖锐的带边缘，在 20 V 的偏压下具有~1 A/W 的峰值响应度。