Theory of Raman spectra of heavily doped semiconductor multiple quantum wells.

Abstract

We present theoretical studies of the Raman spectra of heavily doped GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As multiple quantum wells in an attempt to understand the effects of heavy two-dimensional (2D) doping on the electronic structures and optical properties of semiconductors. Samples of GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As multiple quantum wells with x=0.2 and 0.4, well-barrier widths around 100 \AA{}, and 2D electron densities up to more than 1\ifmmode\times\else\texttimes\fi{}${10}^{13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ are examined. Intersubband and intrasubband Raman plasmon modes are calculated with an energy-dependent effective-mass theory, which takes into account the band nonparabolicity. The screened external potential due to impurity and electron charge distribution including the exchange and correlation effects are calculated self-consistently within the local-density approximation. The resulting Raman spectra are found to be sensitive to the shape of the screened potential, and they are in qualitative agreement with experimental data. \textcopyright{} 1996 The American Physical Society.