SPATIAL VARIATION OF PLASMON DAMPING NEAR THE POLAR SURFACES OF INAS AND INSB

The behaviour of the conduction band electron plasmon at the polar sur faces 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 pla smon 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 m easured HREEL spectra. This spatial variation changes the form of the wavevector-dependence of the damping at different depths below the sur face and in regions where the local plasma frequency varies rapidly wi th depth, In particular, where the plasma frequency varies on signific antly shorter length scales than the effective probing depth and scree ning length, the effective damping becomes very large due to the super position of a wide range of plasma frequencies in the local approximat ion. 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 o f InSb(001) depletion layers and weaker InAs(001) accumulation layers. (C) 1998 Published by Elsevier Science B.V. All rights reserved.