Fast Recovery of Excitonic Absorption Peaks in Tunneling Bi-Quantum-Well Structures

Fast recovery of the excitonic absorption peak in “tunneling bi-quantum-well structures” is proposed and demonstrated for the first time. A tunneling bi-quantum-well consists of the repeated structure of narrow and wide wells coupled quantum-mechanically, enabling photo-excited carriers in the narrow well to tunnel toward the wide well with a relaxation time much faster than the radiative recombination time of carriers. The recovery time was reduced to 18 ps using the 4.0 nm-thick tunneling barrier and strongly depends on the barrier thickness as would be expected from electron tunneling.