Photoinduced bulk-surface dynamics: time resolved two photon photoemission signals at semiconductor surfaces

A free particle theory of photoinduced bulk-surface dynamics at semiconductor surfaces is developed wherein relaxation processes arising from electron–electron and electron–phonon scattering are treated phenomenologically. The role played by bulk-surface dynamics in the thermalization and cooling processes of the bulk and the complementary issue of how bulk dynamics influences the surface state occupancy are both studied. Time resolved 2PPE spectra is analysed both in the context of pure bulk as well as combined bulk-surface dynamics and its relation to the time dependent populations in the conduction band and surface states is discussed.