Dresden 2003 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 32: Spinabh
ängiger Transport II

HL 32.2: Vortrag

Mittwoch, 26. März 2003, 14:45–15:00, POT/81

Spin relaxation times measured by spatially resolved Faraday rotation — •Markus Beck, Jochen Müller, Stefan Malzer, Claus Metzner, and Gottfried H. Döhler — Institut für Technische Physik I, Universität Erlangen Nürnberg, Erlangen, Germany

A common approach for the determination of spin relaxation times in semiconductors is time resolved Faraday rotation using femtosecond pump and probe measurements. This method is limited to spin relaxation times which do not exceed the laser repetition rate (typically 12 ns) significantly.

Instead of using a femtosecond laser, we measure the Faraday rotation with two cw laser diodes spatially resolved. One diode excites a stationary distribution of carriers, whereas with the second one, we probe the spin polarization, making use of the Faraday rotation. Knowing the transport properties and the resulting stationary carrier distribution, the relaxation time can be determined from the spatially resolved Faraday rotation.

We have measured spin relaxation times in InGaAs quantum wells and in GaAs. The influence of carrier density, modulation doping and external fields will be discussed.

An additional advantage of using cw lasers is the higher spectral resolution and the possibility to choose pump and probe photon energies independently. Hence, detailed information about the Faraday rotation can be obtained. This topic will be presented in a further contribution.