PHOTOLUMINESCENCE STUDY OF ELECTRON-TUNNELING TRANSFER IN COUPLED-QUANTUM-WELL STRUCTURES

We have investigated the processes of electron tunneling between the f irst two states in asymmetric coupled-quantum-well structures using ti me-resolved photoluminescence spectroscopy. The rates of electron tunn eling 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 differenc e between the initial and final states in the transfer process, which can be measured as the energy difference between the direct and indire ct recombinations at the maximum electron tunneling transfer rate, it is shown that this tunneling transfer process is closely related to in terface roughness. The electron tunneling transfer rates obtained expe rimentally are compared with the intersubband scattering rates calcula ted taking various scattering processes into account and it is found t hat the tunneling rates are predominantly determined by interface roug hness. Furthermore, the rate of tunneling transfer is found to decreas e as the temperature increases from 3 to 40 K. This temperature depend ence is discussed in terms of the exciton/electron population ratio in the wide well. (C) 1995 American Institute of Physics.