Observation of an optical switching effect in GaAs/AlGaAs quantum wells under hydrostatic pressure

We have observed extremely sharp (\u394 \u2dc 0.01 meV) discontinuities in the photoluminescence excitation (PLE) spectra of GaAs/Al\u2093Ga\u2081\u208b\u2093As single quantum wells under hydrostatic pressure at low temperatures. 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 single peak for excitation energies on the other side. The lower energy peak of the doublet is completely quenched on the other side of the discontinuity, which means that by changing the excitation photon energy slightly, the PL mechanism responsible for the lower energy peak can be switched on and off. The dependence of this phenomenon on pressure, temperature, and the excitation laser intensity has been investigated for a 70 \uc5 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 \u2dc17\u201325 kbar, at low temperature ( 7227 K), and at a moderately high (>4 W/cm2) excitation laser intensity.NRC publication: Ye