Study of photomodulation dynamics of excitonic reflectivity in GaAs/AlAs quantum well heterostructures

The spectral, temperature and time dependences of photoinduced changes of type-l excitonic transitions in GaAs/AlAs single QW structures were studied using wavelength-modulated reflectance spectroscopy. It was revealed that photoinduced changes of exciton spectra are closely related to the photoexcitation and redistribution of photocarriers in the QW region. It was obtained that the decay of photoinduced changes occurs in the millisecond range at 300 K and in the second range at 90 K. The temperature dependence of decay time is discussed in terms of both tunneling and thermal emission of photo-excited carriers from the QW.