Optical probing of spin dynamics of two-dimensional and bulk electrons in a GaAs/AlGaAs heterojunction system

The electron spin dynamics in a GaAs/AlGaAs heterojunction system containing a high-mobility two-dimensional electron gas (2DEG) have been studied in this paper by using pump-probe time-resolved Kerr rotation experiments. Owing to the complex layer structure of this material, the transient Kerr response contains information about electron spins in the 2DEG, an epilayer and the substrate. We analyzed the physics that underlies this Kerr response, and established the conditions under which it is possible to unravel the signatures of the various photo-induced spin populations. This was used to explore how the electron spin dynamics of the various populations depend on the temperature, magnetic field and pump-photon density. The results show that the D'Yakonov-Perel' mechanism for spin dephasing (by spin-orbit fields) plays a prominent role in both the 2DEG and bulk populations over a wide range of temperatures and magnetic fields. Our results are of importance for future studies on the 2DEG in this type of heterojunction system, which offers interesting possibilities for spin manipulation and control of spin relaxation via tunable spin-orbit effects.