Cathodoluminescence spectroscopy of ambipolar diffusion in (Al,Ga)As barriers and capture of nonequilibrium carriers in GaAs quantum wells

Ambipolar vertical diffusion of carriers generated in an Al0.3Ga0.7As barrier is investigated by cathodoluminescence (CL) spectroscopy in a system containing a sequence of GaAs-based quantum wells (QWs). The intensity distribution of the CL line scan exhibits a single exponential decay for the first QW of the sequence, reflecting a pure diffusion-limited transport. However, the CL line scans of the second, third, and fourth QWs are governed by diffusion only for large separations between the electron beam and the corresponding QW. For smaller distances, the CL intensity distribution is significantly influenced by the carrier capture into the intervening QWs. (c) 2008 American Institute of Physics.