Ultrafast coherent and incoherent dynamics of intersubband excitations in quasi-two-dimensional semiconductors

Thomas Elsaesser, Robert A. Kaindl, Stephan Lutgen, Michael Woerner, Andreas Hase, Harald Künzel

Research output: Contribution to journalConference articlepeer-review


Intersubband excitations play an important role for ultrafast carrier dynamics in quasi-two-dimensional semiconductors and for device applications. We present a study of the ultrafast coherent and incoherent dynamics of intersubband excitations in a pure electron plasma by means of femtosecond spectroscopy in the mid-infrared. The different relaxation processes following intersubband excitation of electrons in GaInAs/AlInAs quantum wells are observed in real-time and the relevant microscopic scattering mechanisms are identified. We find a decay of coherent intersubband polarizations on a time scale of several hundreds of femtoseconds which is governed by electron-electron scattering. Electrons excited to the n=2 conduction subband undergo intersubband scattering to the n=l subband by emission of longitudinal optical phonons with characteristic time constants of l ps. This is followed by thermalization of the backscattered electrons on a similar time scale, involving both electron-electron and electron-phonon scattering. Eventually, the hot electron distribution cools down to lattice temperature within about 50 ps.

Original languageEnglish (US)
Pages (from-to)2-9
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1998
Externally publishedYes
EventUltrafast Phenomena in Semiconductors II - San Jose, CA, United States
Duration: Jan 28 1998Jan 29 1998


  • Cooling
  • Femtosecond spectroscopy
  • Intersubband excitation
  • Phase relaxation
  • Scattering of electrons
  • Thermalization
  • Ultrafast carrier dynamics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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