Modification of the coupling of double quantum wells through band structure changes under hydrostatic pressure

We have investigated the energies of the electronic states in a series of GaAsAl _xGa _1-xAs double quantum wells (with thicknesses to give uncoupled and coupled well wave functions) as a function of the band structures of the component materials as modified by hydrostatic pressures up to 40 kbars. Photoluminescence excitation (PLE) spectra at high pressures measured at 4 K and 77 K have been interpreted in terms of the established band offsets and the known pressure shifts of the bulk Γ and X bands. The pressure coefficients of the energies of allowed transitions between the quantized states of the wide uncoupled wells measured are all equal to the pressure coefficient of the bulk GaAs band gap. For coupled wells, the energies of the allowed transitions all show a decrease in their pressure coefficients near 20 kbar. The allowed transitions of the coupled wells are split into doublets due to coupling and these splittings showed changes near 20 kbar. We tentatively ascribe band mixing as primarily responsible for these effects.