Optical generation of spatially separated electron and hole gases in intrinsic ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ double quantum wells

We show that optical excitation of a wide GaAs quantum well, which is located close to the sample surface, can give rise to the creation of a high-density two-dimensional hole gas in the well. Based on this mechanism, we present a double quantum well structure in which spatially separated electron and hole gases are optically created at close proximity $\left(\sim 20\hspace{0.5em}\mathrm{nm}\right).\mathrm{}$ We demonstrate how the density of each gas can be independently controlled by the intensity of the exciting lasers.