Optical and electrical properties of narrow gap germanium-tin alloys with high tin contents for middle and far infrared applications
| Author(s) | Imbrenda, Dominic | |
| Date Accessioned | 2018-12-14T13:39:05Z | |
| Date Available | 2018-12-14T13:39:05Z | |
| Publication Date | 2018 | |
| SWORD Update | 2018-10-17T16:05:00Z | |
| Abstract | Germanium-Tin (GeSn) alloys have received considerable attention because of the interesting electronic properties they possess. The offer a potential route to a direct bandgap group IV semiconductor that is isoelectronic with silicon and can be fully integrated into current silicon manufacturing processes. Despite the active research of GeSn some of their optical and electrical properties, especially for the high Sn contents, are not fully understood. ☐ During the course of this research, the optical properties of high Sn content GeSn thin film alloys deposited directly on Ge were determined by variable angle spectroscopic ellipsometry (VASE) from the ultraviolet into the infrared (0.190 – 6 µm). For the first time, the complex dielectric function, complex index of refraction, and absorption coefficient of GeSn alloys with atomic Sn percentages from 15- 27%, are presented. The characterization of the optical properties is important in itself for the development of novel devices but more importantly, they also contain rich information about the electronic bandstructure. Analyzing the second derivative of the dielectric function enables the determination of the energy levels of the critical point transitions in the electronic bandstructure. Second derivative analysis results of the high Sn content films are compared to theoretical predictions and expand on the current predictive models. ☐ Weyl semimetals are a new topological state of matter in semimetals without either spatial inversion or time-reversal symmetry, are characterized by their zero-energy, direct bandgaps, and exhibit novel electronic properties. An active area of research is to determine whether certain materials exhibit the characteristics of a Weyl semimetal. The Sn percentage at which the direct bandgap of GeSn reaches zero is roughly 27%, making it a candidate for a Weyl semimetal at this high Sn percentage. Likely signatures of Weyl semimetals are negative magnetoresistance and photogalvanic current from circularly polarized light. Details and results of these experiments conducted on GeSn are given. Although the results are inconclusive, they open the possibility that high Sn content GeSn alloys belong to this exciting new class of materials. | en_US |
| Advisor | Kolodzey, James | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Electrical and Computer Engineering | |
| DOI | https://doi.org/10.58088/bxhr-xp30 | |
| Unique Identifier | 1078921879 | |
| URL | http://udspace.udel.edu/handle/19716/23993 | |
| Language | en | |
| Publisher | University of Delaware | en_US |
| URI | ||
| Keywords | Pure sciences | en_US |
| Keywords | Applied sciences | en_US |
| Keywords | Physical sciences | en_US |
| Keywords | Dielectric function | en_US |
| Keywords | Ellipsometry | en_US |
| Keywords | Semiconductors | en_US |
| Title | Optical and electrical properties of narrow gap germanium-tin alloys with high tin contents for middle and far infrared applications | en_US |
| Type | Thesis | en_US |