The exciton photoluminescence and vertical transport of photoinduced carriers in CdSe/CdMgSe superlattices

摘要

The photoluminescence and photoluminescence excitation spectra, phonon-related Raman scattering, and vertical transport of photoinduced carriers and excitons along the growth direction in type 1 low-strained CdSe/CdMgSe superlattices, which are grown on InAs substrates using molecular-beam epitaxy, are studied for the first time. The studies are carried out at various temperatures and excitation intensities. The vertical transport is studied by a purely optical method involving an enlarged quantum well built in into the superlattice. This well serves as a sink for the excitons and charge carriers tunneled through the superlattice. At 2-150 K, the carriers are preferentially transported by free excitons. However, in superlattices with periods of 5.9 and 7.3 nm, this transport is not of the Bloch type. A comparison of the calculated energies of the band-to-band transitions in the superlattices with the experimental data yields the relative magnitude of the valence-band offset in the range 0.4-0.5. The Raman spectra indicate that the behavior of optical phonons in CdMgSe is bimodal. (c) 2005 Pleiades Publishing, Inc.