dc voltage effect on elementary excitations of a two-dimensional electron gas

Using a generalized self-consistent field theory we obtained the intersubband spectra of charge-density excitations for the nonuniform electron gas of a ${\mathrm{GaAs}\text{−}\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ single quantum well submitted to dc gate voltages. The simulations performed with incoming laser light in extreme resonance conditions with the split-off gap of the $\mathrm{GaAs}$ demonstrate the collective character of the single-particle excitations and the different regimes of coupling between the charge-density excitations and the longitudinal optical phonon of $\mathrm{GaAs}$.

Figure 1

The calculated potential profiles of a one side gated modulation-doped quantum well with gate voltages, $V_g=-360,-280,-200,-80,0,80,200,280$ and $360\mathrm{mV}$.

Figure 2

Calculated 2D electronic density in the well in function of the same gate voltages of Fig. 1.

Figure 3

Calculated subbands energy dispersions and electronic density of the quantum well in function of the same gate voltages of Fig. 1.

Figure 4

Calculated subband energy transitions as a function of the same gate voltages of Fig. 1.

Figure 5

Calculated polarized resonant Raman spectra of the QW as a function of selected gate voltages showing the spectral lines of the collective (CDE) and single-particle (SPE) excitations for incident laser energy of $1.945\mathrm{eV}$.

Figure 6

Calculated polarized resonant Raman spectra of the QW as a function of selected gate voltages showing the merging of the ${\mathrm{CDE}}_{02}^{+}$ and ${\mathrm{SPE}}_{02}$ peaks when the extreme resonance regime is left. Other excitations are also shown.