Energy-resolved study of the spin precession in photoemission from activated (110) GaAs

The measurement of the spin vector S of electrons photoemitted from a III-V compound semiconductor activated to negative electron affinity is shown to be a powerful means to explore band hybridization properties, surface effects, and to estimate characteristic times of electron relaxation. Because of the lack of inversion symmetry (i.e., to the conduction-band spin splitting), an internal spin precession occurs in the bulk semiconductor and also in the band-bending region (BBR) near the surface. From the modulus of S we determine the hot-electron mean free path. From the S direction we deduce the angle of spin precession ${\theta }_p$ due to the internal precession vector ω. The experimental originality of the present work stands in the combination of the S measurement with the high-resolution energy analysis of the photoemitted electrons. The dependence of ${\theta }_p$ on the electron kinetic energy reflects the memory of the initial anisotropic distribution of electron momenta, and its modifications during thermalization and transit through the BBR. Our analysis relates the D’ymnikov-D’yakonov-Perel’ formalism for the calculation of spin-polarization properties under circularly polarized light excitation with the widely used Kane k⋅p? band description.