title: Measurement and modeling of ultrafast carrier dynamics and transport in germanium/silicon-germanium quantum wells.
abstract: We measure the intervalley scattering time of electrons in the conduction band of Ge quantum wells from the direct Γ valley to the indirect L valley to be ~185 fs using a pump-probe setup at 1570 nm. We relate this to the width of the exciton peak seen in the absorption spectra of this material, and show that these quantum wells could be used as a fast saturable absorber with a saturation fluence between 0.11 and 0.27 pJ/μm. We also observe field screening by photogenerated carriers in the material on longer timescales. We model this field screening by incorporating carrier escape from the quantum wells, drift across the intrinsic region, and recovery of the applied voltage through diffusive conduction.
authors.affiliation: Edward L Ginzton Laboratory, Stanford University, 348 Via Pueblo Mall, Stanford, CA 94305, USA. sclaussen@stanford.edu
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Claussen
authors.forename: Emel
authors.initials: E
authors.lastname: Tasyurek
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Roth
authors.forename: David A B
authors.initials: DA
authors.lastname: Miller
mesh_terms: D017076:Computer-Aided Design; D004579:Electron Transport; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005857:Germanium / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D008956:Models, Chemical; D045663:Quantum Dots; D011789:Quantum Theory; D012666:Semiconductors; D012825:Silicon / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D005857:Germanium; D012825:Silicon