Energy-Resolved Electron-Spin Dynamics at Surfaces of p-Doped GaAs

Electron-spin relaxation at different surfaces of p-doped GaAs is investigated by means of spin, time, and energy-resolved two-photon photoemission. These results are contrasted with bulk results obtained by timeresolved Faraday rotation measurements as well as calculations of the Bir-Aronov-Pikus spin-flip mechanism. Due to the reduced hole density in the band bending region at the 100 surface the spin-relaxation time increases over two orders of magnitude towards lower energies. At the flat-band 011 surface a constant spin relaxation time in agreement with our measurements and calculations for bulk GaAs is obtained.