Spatial variation of plasmon damping near the polar surfaces of InAs and InSb

The behaviour of the conduction band electron plasmon at the polar surfaces of InAs and InSb has been investigated using HREELS measurements combined with local dielectric theory simulations and charge profile calculations. Specific emphasis has been placed on the role of the plasmon damping in determining the observed spectra of excitations. It is found that significant spatial variation of the plasmon damping must be incorporated into the dielectric models in order to reproduce the measured HREEL spectra. This spatial variation changes the form of the wavevector-dependence of the damping at different depths below the surface and in regions where the local plasma frequency varies rapidly with depth, In particular, where the plasma frequency varies on significantly shorter length scales than the effective probing depth and screening length, the effective damping becomes very large due to the superposition of a wide range of plasma frequencies in the local approximation. This "structural" damping is therefore very different in origin from the usual Landau damping and momentum scattering mechanisms. The effect of plasmon damping within the accumulation layer at InAs(111)A surfaces is investigated and compared with the inhomogeneous region of InSb(001) depletion layers and weaker InAs(001) accumulation layers. (C) 1998 Published by Elsevier Science B.V. All rights reserved.