Date of Award
Master of Science
Department of Engineering Physics
John W. McClory, PhD
GeSn is a promising material for photodiodes in the near-to-mid infrared (IR) spectrum because of new growth methods that enable integration with complementary metal oxide semiconductor (CMOS) technology. While natural germanium has a threshold wavelength of 1800 nm, 6.9 Sn content extends the threshold wavelength to 2700 nm based on a Sn content dependent bandgap. Also, unlike other semiconductors that require liquid nitrogen cooling to act as an IR sensor, GeSn can be operated at room temperature, enabling a wide variety of applications. In this study, photodiodes ranging from 0 to 6.9 tin content were subjected to 1 MeV (Si) equivalent neutron radiation ranging from 4 1012 cm2 to 4 1014 cm2. IV curves, CV curves, and relative photoresponse were measured before and after irradiation to observe change due to displacement damage. While the change in IV measurements varied widely, the photoresponse more than doubled for all irradiated samples, contrary to expectation. The samples of low tin content had a greater increase (as much as 1100 ) than high tin content samples (ranging from 100 to 400 ). Deep-level transient Fourier spectroscopy (DLTFS) was also used to measuredefect levels. The 0 and 6.8 tin samples showed defects at energies of 0.26 eV below the conduction band and 0.17 eV above the valence band, respectively. The 0.26 eV trap is attributed to an A center vacancy-oxygen (V-O) complex and the 0.17 eV trap is attributed to a vacancy-phosphorous (V-P) defect.
DTIC Accession Number
Gale, Nathan J., "Neutron Displacement Damage in Germanium Tin Photodiodes" (2020). Theses and Dissertations. 3596.