Ellipsometric investigation of optical constant and energy band gap of Zn1−xMnxSe/GaAs (100) epilayers

Kim, D.-J.; Yu, Young‐Moon; Choi, Yong Dae; Lee, J.-W.

doi:10.1016/j.apsusc.2005.07.037

Cited by 3 publications

(1 citation statement)

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“…Spectroscopic ellipsometry has proven to be useful in extracting the material microstructure in the form of surface features, the index of refraction below the band gap, and the critical point features above the band gap. [27][28][29] Transmission and reflection measurements have been widely used to determine the band gap values of materials, 18,19,30 but generally lack sensitivity to the material microstructure. A comparison between spectroscopic ellipsometry and UV-Vis spectroscopy measurements highlights the relative strengths and weaknesses of the two techniques.…”

Section: Comparison Between Uv-vis and Ellipsometrymentioning

confidence: 99%

Band gap and structure of single crystal BiI3: Resolving discrepancies in literature

Podraza

Qiu

Hinojosa

et al. 2013

Journal of Applied Physics

125

106

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Bismuth tri-iodide (BiI3) is an intermediate band gap semiconductor with potential for room temperature gamma-ray detection applications. Remarkably, very different band gap characteristics and values of BiI3 have been reported in literature, which may be attributed to its complicated layered structure with strongly bound BiI6 octahedra held together by weak van der Waals interactions. Here, to resolve this discrepancy, the band gap of BiI3 was characterized through optical and computational methods and differences among previously reported values are discussed. Unpolarized transmittance and reflectance spectra in the visible to near ultraviolet (UV-Vis) range at room temperature yielded an indirect band gap of 1.67 ± 0.09 eV, while spectroscopic ellipsometry detected a direct band gap at 1.96 ± 0.05 eV and higher energy critical point features. The discrepancy between the UV-Vis and ellipsometry results originates from the low optical absorption coefficients (α ∼ 102 cm−1) of BiI3 that renders reflection-based ellipsometry insensitive to the indirect gap for this material. Further, electronic-structure calculations of the band structure by density functional theory methods are also consistent with the presence of an indirect band gap of 1.55 eV in BiI3. Based on this, an indirect band gap with a value of 1.67 ± 0.09 eV is considered to best represent the band gap structure and value for single crystal BiI3.

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