Effect of spatial localization of dopant atoms on the spacing of electron subbands in δ-doped GaAs:Si

Using Raman spectroscopy we have investigated the spacing of the electron subbands in nominally δ-doped GaAs structures which show a considerable spread of the silicon dopant atoms along the growth direction. For optical excitation in resonance with the E0+Δ0band gap, spin-density intersubband excitations are observed. For excitation in resonance with the E1 band gap we find a strong enhancement of scattering by collective intersubband plasmon-phonon modes. The measured energy spacings between the electron subbands deviate significantly from what is expected for ideal δ doping. Self-consistent electronic subband calculations taking into account the spread of the dopant atoms along the growth direction, in contrast, yield a good quantitative agreement between calculated and measured subband spacings. This demonstrates the potential of intersubband Raman spectroscopy for the analysis of the spatial localization of dopant atoms in δ-doped structures.