OBSERVATION OF AN OPTICAL SWITCHING EFFECT IN GAAS ALGAAS QUANTUM-WELLS UNDER HYDROSTATIC-PRESSURE/

We have observed extremely sharp (Delta similar to 0.01 meV) discontin uities in the photoluminescence excitation (PLE) spectra of GaAs/AlxGa 1-xAs single quantum wells under hydrostatic pressure at low temperatu res. These discontinuities are found to originate from abrupt changes in the photoluminescence (PL) spectrum as a function of the excitation energy. Near each discontinuity, the PL spectrum shows a doublet for excitation energies on one side of the discontinuity, and only a singl e peak for excitation energies on the other side. The lower energy pea k of the doublet is completely quenched on the other side of the disco ntinuity, which means that by changing the excitation photon energy sl ightly, the PL mechanism responsible for the lower energy peak can be switched on and off. The dependence of this phenomenon on pressure, te mperature, and the excitation laser intensity has been investigated fo r a 70 Angstrom quantum well. The energies of these discontinuities in the PLE spectrum have similar pressure coefficients to the GaAs band gap energy, and are observed only in the pressure range of similar to 17-25 kbar, at low temperature (less than or similar to 27 K), and at a moderately high (> 4 W/cm(2)) excitation laser intensity.