Optical studies of impurity trapping at the GaAlAs/GaAs interface in quantum well structures

We present low-temperature photoluminescence studies of nominally undoped GaAs quantum wells in which weak acceptor-related emissions can be observed. We investigate the influence of different sequences of prelayers, in which the number and the aluminum concentration of the layers are varied, on the impurity concentration in the quantum well, and show that thin layers of low aluminum percentage act as very efficient impurity trapping centers. We also present calculations of the electron to acceptor photoluminescence line shape, which show that the acceptor distribution has its maximum at the well interface, extending about 7 Å in the barrier and 12 to 30 Å in the well.