Collective excitations in the accumulation layer of InAs(110): Nonlocal response theory

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Abstract
We discuss plasmon and phonon modes in the accumulation layer of a model semiconductor with the aid of calculations based on a nonlocal description of dielectric response in the random-phase approximation. The first model we consider is that of a polarizable jellium slab at finite temperature with surface charges that bend the bands downward; lattice vibrations are ignored. Choosing model parameters appropriate to lightly doped InAs(110) at room temperature, we obtain intersubband as well as intrasubband plasmons and discuss their dispersion relations, localization, and line shapes. Evidence for two-dimensional and ‘‘acoustic’’ plasmons is presented: dispersion relations that have square-root and linear behavior at long wavelengths, respectively. All plasmon modes are strongly damped when their dispersion curves enter the single-particle continua. When the dynamical response of the lattice is included in the model, we obtain coupled plasmon-phonon modes or ‘‘plasmarons’’ and study their dispersion and line shapes. Our results confirm and extend the interpretation of high-resolution electron-energy-loss spectroscopy data reported recently for InAs(110) exposed to atomic hydrogen.