Photoluminescence study of electron tunneling transfer in coupled-quantum-well structures

Abstract

We have investigated the processes of electron tunneling between the first two states in asymmetric coupled-quantum-well structures using time-resolved photoluminescence spectroscopy. The rates of electron tunneling transfer from a wide to a narrow well are derived from the decay times of the photoluminescence from the wide well at various electric fields. It is confirmed that the transfer is enhanced at the electric-field value where the exciton energy in the wide well is equal to the electron energy in the narrow well. By analyzing the energy difference between the initial and final states in the transfer process, which can be measured as the energy difference between the direct and indirect recombinations at the maximum electron tunneling transfer rate, it is shown that this tunneling transfer process is closely related to interface roughness. The electron tunneling transfer rates obtained experimentally are compared with the intersubband scattering rates calculated taking various scattering processes into account and it is found that the tunneling rates are predominantly determined by interface roughness. Furthermore, the rate of tunneling transfer is found to decrease as the temperature increases from 3 to 40 K. This temperature dependence is discussed in terms of the exciton/electron population ratio in the wide well.