Elementary excitations at doped polar semiconductor surfaces with carrier-depletion layers

We make a comparative analysis of coupled carrier plasmon±polar phonon modes at doped polar semiconductor surfaces in the absence and the presence of a carrier-depletion layer. Our analysis shows how the effect of the depletion layer appears in the spatial structure of each excitation mode visualized in a contour map of the induced charge-density, the coupling character elucidated by the phase relation and the amplitude ratio of the carrier component and the polar-phonon component in the induced charge-density distribution, and the energy-loss intensity due to the surface excitation. # 2001 Elsevier Science B.V. All rights reserved