Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 53: Ultra fast phenomena

HL 53.7: Talk

Friday, March 30, 2007, 12:30–12:45, H15

Ultrafast electron relaxation-dynamics in p-doped GaAs — •Yao-Hui Zhu, Hans Christian Schneider, and Martin Aeschlimann — Fachbereich Physik, TU Kaiserslautern, 67663 Kaiserslautern

Ultrafast electron dynamics in p-doped GaAs is studied by energy- and time-resolved two-photon-photoemission (2PPE). Using this surface sensitive technique allows one to study the carrier dynamics over a wide energy range in the band-bending region at (001) surfaces. Electron relaxation-dynamics is monitored by measuring the energy distribution of photoemitted electrons after an initial nonequilibrium electron distribution has been created by the ultrashort pump laser up to 2 eV above the conduction band minimum. To separate the contributions of the degenerate pump and probe beams to the photoemitted electrons, an electron spin-analyzer and different light polarizations and are used.

The dependence of the observed electron dynamics on the excitation energy is explained well by Boltzmann equation calculations that take into account the carrier-carrier Coulomb interaction. It is found that electron relaxation by scattering of heavy holes into the light-hole band is dominant for the electron relaxation process. Moreover, dynamic screening is crucial for the relaxation of the highly excited electrons at a doping density of 1× 10¹⁹ cm⁻³.