Infrared dielectric response, index of refraction, and absorption of germanium-tin alloys with tin contents up to 27% deposited by molecular beam epitaxy
Abstract
The dielectric spectral response of Ge1-xSnx thin film alloys with relatively high Sn contents (0.15 ≤ x ≤ 0.27) and thickness from 42 to 132 nm was characterized by variable angle spectroscopic ellipsometry over the wavelength range from 0.190 to 6 μm. The Ge1-xSnx thin films were deposited on Ge substrates by molecular beam epitaxy using an electron-beam source for Ge to achieve a substrate temperature below 150 °C to prevent the surface segregation of Sn. From the measured dielectric function, the complex refractive index was calculated indicating an increase in the real index with the Sn content at mid-infrared wavelengths. The ellipsometry revealed that the band structure critical point energies red-shifted with the increasing Sn content. The optical absorption coefficient was calculated from the imaginary index and showed a strong absorption into, and beyond, the mid-infrared with the increasing Sn content.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 17, 2018
- Source ID
- 10.1063/1.5040853
Entities
People
- Dominic Imbrenda
- J. Kolodzey
- Jeremy Vanderslice
- Nalin S. Fernando
- Rigo A. Carrasco
- Ryan Hickey
- Stefan Zollner
Organizations
- Air Force Office of Scientific Research
- Army Research Office
- National Science Foundation
- New Mexico State University
- University of Delaware