Optical bandgap of single- and multi-layered amorphous germanium ultra-thin films
- Department of Physics and School of Engineering, Brown University, 182-184 Hope St., Providence, Rhode Island 02912 (United States)
- Gatan, Inc., 5794 W Las Positas Blvd., Pleasanton, California 94588 (United States)
- School of Engineering, Brown University, 184 Hope St., Providence, Rhode Island 02912 (United States)
Accurate optical methods are required to determine the energy bandgap of amorphous semiconductors and elucidate the role of quantum confinement in nanometer-scale, ultra-thin absorbing layers. Here, we provide a critical comparison between well-established methods that are generally employed to determine the optical bandgap of thin-film amorphous semiconductors, starting from normal-incidence reflectance and transmittance measurements. First, we demonstrate that a more accurate estimate of the optical bandgap can be achieved by using a multiple-reflection interference model. We show that this model generates more reliable results compared to the widely accepted single-pass absorption method. Second, we compare two most representative methods (Tauc and Cody plots) that are extensively used to determine the optical bandgap of thin-film amorphous semiconductors starting from the extracted absorption coefficient. Analysis of the experimental absorption data acquired for ultra-thin amorphous germanium (a-Ge) layers demonstrates that the Cody model is able to provide a less ambiguous energy bandgap value. Finally, we apply our proposed method to experimentally determine the optical bandgap of a-Ge/SiO{sub 2} superlattices with single and multiple a-Ge layers down to 2 nm thickness.
- OSTI ID:
- 22494858
- Journal Information:
- Journal of Applied Physics, Vol. 119, Issue 1; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
Similar Records
Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD
Ge interface engineering using ultra-thin La{sub 2}O{sub 3} and Y{sub 2}O{sub 3} films: A study into the effect of deposition temperature