EXCITATION-INTENSITY-DEPENDENT PHOTOLUMINESCENCE QUENCHING DUE TO ELECTRIC-FIELD SCREENING BY PHOTOCARRIERS CAPTURED IN SINGLE-QUANTUM-WELLSTRUCTURES

The radiative recombination efficiency of single-quantum-well (SQW) st ructures in the presence of an electric field was found to be strongly dependent on the density of carriers present in the well. This was ev idenced by measuring the wavelength-integrated intensity of the photol uminescence (PL) emitted by the excitonic ground-state transition in I nxGa1-xAs/GaAs SQW's, as a function of the electric field applied thro ugh a semitransparent Schottky electrode, for various excitation inten sities. We attribute this excitation-intensity-dependent PL quenching to a local flattening of the bands in the well region induced by the s creening of the carriers trapped in the well. This photocarrier screen ing of the electric field in the well region affects the dependence of the PL on the excitation intensity (I(PL) is-proportional-to I(ex)gam ma). We also show how this effect can lead to switching of a modulated PL signal using a dc excitation source with enhancement factor in the modulated component exceeding 19 for appropriate applied voltages and excitation intensities.