Raman spectroscopic assessment of laterally structured δ-doped GaAs: Si

Abstract

Laterally structured Si δ-doped GaAs has been investigated by photoluminescence and Raman spectroscopy. Wires were fabricated by electron beam lithography followed by reactive ion mesa etching. Radiative recombination across the E 0 + Δ 0 band gap is observed down to the narrowest wire width of 150 nm indicating the presence of an electron gas even in those structures. Collective intersubband plasmon-phonon modes measured by inelastic light scattering exhibit a down-shift in energy which indicates a reduction of the free carrier concentration caused by electron traps in the sidewalls. Spin-density excitation energies, by contrast, which give essentially the energy spacings of the electron subbands formed in the quasi-two-dimensional electron gas associated with the δ-doping layer, show a slight shift to higher energies possibly due to a rearrangement of the electron subbands caused by the additional lateral confinement.