Observation of intensity-dependent excitonic emission linewidth broadening in periodic asymmetric coupled three narrow quantum wells

By taking the advantage of an extremely narrow excitonic emission linewidth in a sample of periodic asymmetric coupled three narrow quantum wells, we report our first observation of the broadening of the photoluminescence excitonic linewidth under the low excitation intensities: 0.54 W/cm/sup 2/-1.6 kW/cm/sup 2/ at low temperature. The sample was grown by MBE on a semi-insulating GaAs substrate. The expitaxial layers consist of 10 periods, each of which is composed of three narrow asymmetric coupled GaAs quantum wells with the designed thicknesses of45 /spl Aring/, 30 /spl Aring/, and 50 /spl Aring/ coupled by 40 /spl Aring/ Al/sub 0.3/Ga/sub 0.7/As barriers. We measured photoluminescence excitation spectra in the temperature range of4 K - 300 K.<
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