Temperature-dependent plasmons in InSb

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Abstract
The temperature dependence of the conduction-band plasmon excitation in doped InSb has been measured by high-resolution electron energy loss spectroscopy (HREELS). Previous measurements, carried out at 300 K, have shown that preparation of the (100) surface of p-type InSb, by low-energy ion bombardment and annealing, leads to a near-surface region having a so-called depletion layer of approximately 200 AA caused by Fermi level pinning at the surface. Below this, an n-type layer extends a further 500 AA into the material arising because of the ion-induced damage. Measurements of the plasmon energy reported here indicate an asymmetric broadening giving rise to an apparent shift of about 7 meV to lower energy as the surface temperature is raised from about 200-470 K. More significant is a large increase in the intensity of the plasmon between 300 and 470 K. By using model calculations, based on dielectric theory, the authors interpret these results in terms of an increased contribution to the conduction-band free-carrier concentration leading to a reduction in the thickness of the depletion layer.