TUNNELING AND RELAXATION IN COUPLED QUANTUM-WELLS

We study by time-resolved luminescence, with subpicosecond resolution, the tunnelling processes out of a narrow well (NW) coupled to a wider one 0 by a thin barrier. Resonance and nonresonance between the first level of the NW and the second level of the WW is obtained by adjusting the WW width. At resonance, and for narrow enough barriers, the transfer of the electrons to the WW ground state takes about 2ps and is analogous to LO phonon-assisted intersubband relaxation. When the barrier thickness is increased, even at resonance, the transfer time from the NW to the WW varies exponentially with the barrier thickness, as in the nonresonant case, showing that the coherence of the coupled states is destroyed. © 1990 The Japan Society of Applied Physics.