Femtosecond interband hole scattering in Ge studied by pump-probe reflectivity

• Published in: Solid state communications Vol. 104; no. 1; pp. 51 - 55
• Main Authors: Zollner, Stefan, Myers, K.D., Jensen, K.G., Dolan, J.M., Bailey, D.W., Stanton, C.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-10-1997; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity); Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Monte Carlo method; Band structure; Semiconductor materials; Drude model; Theoretical study; Optical pumping; Transients; Deformation potential; Reflection spectrum; Electron phonon interaction; Laser radiation; Germanium; Holes; Matrix elements
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/S0038-1098(97)00068-9

We have measured the transient reflectivity changes of bulk Ge after excitation with 140 fs laser pulses at 1.5 eV. The electron and hole dynamics are calculated using an ensemble Monte Carlo method. We find that the observed reflectivity changes are due to three main mechanisms: diffusion, band gap renormalization, and carrier dynamics, particularly scattering of light holes to the heavy hole band via the optical deformation potential interaction. Because of the unique band structure of Ge and the use of a reflectivity technique, we can isolate the role of the light holes with femtosecond time resolution. The Monte Carlo simulation (which uses an optical deformation potential for holes of
d
0=46 eV) overestimates the scattering rate of light holes to the heavy hole band. The agreement can be improved when a lower value for the deformation potential (determined from theory or other experiments) is used.