Home | Employment | Visitors | Members
Spectrally resolved optical study of transient spin dynamics in semiconductors
Year submitted:
2006
Advisor:
Steven T. Cundiff Abstract:
Using the spin of the electron to carry information, instead of or in addi-
tion to its charge, could provide advances in the capabilities of microelectronics.
Successful implementation of spin-based electronics requires preservation of the
electron spin coherence. Long spin coherence times have been observed in lightly
n-doped semiconductors, with a maximum at a “magic” electron density. We sys-
tematically study the spin dynamics of the electron in a GaAs quantum well, where
the electron density in the well can be varied through optical excitation. We show
that spin coherence is lost due to the interplay between localization by disorder
and dynamical scattering. The disorder potential is characterized by measuring
the electron Landé g factor dependence on density. Our results show that the
longest spin coherence is obtained for weakly localized spins, which may dictate
a compromise in the design of devices between increasing the spin coherence time
and improving transport properties.
We also explore the intimate connection between electron spin and optical
excitation that initiates and controls the spin states. We study the interplay of spin
dynamics between excitons, negatively charged excitons and the two-dimensional
electron gas in a lightly n-doped semiconductor quantum well. The spin of the
electron gas can be polarized through interband transitions, and the electron spin
can persist long after the recombination of optically excited carriers. We find
that the excitation of spin polarization of the resident electrons depends on the
recombination times and spin relaxation times of the optically excited carriers and
the energy chosen for the light pulses.
| Attachment | Size |
|---|---|
| chen_thesis.pdf | 2.24 MB |
