quantum wells

Wannier-Stark localization and Bloch oscillations

This chapter discusses the effects of an electric field on the electronic and optical properties of semiconductor superlattices. Here an ideal superlattice is considered to be an infinite periodic series of strongly coupled quantum wells. The …

Electronic energy levels of quantum well wires

An efficient variational method to solve the two‐dimensional Schrödinger equation using a basis set of cubic $B$ splines is introduced. The method, which uses the effective mass theory and the envelope function approximation, is applied to find the …

Miniband formation at finite electric fields in a graded-gap superlattice

We have investigated a graded-gap superlattice with differential photocurrent spectroscopy at 77 K. The lowest conduction subband exhibits with increasing electric field a transition from localized to extended miniband states and back to localized …

Local origin of photocurrent in semiconductor superlattices

To trace the origin of photocurrent (PC) in semiconductor superlatices, we have studied the PC spectra as a function of the applied electric field in a novel compositionally graded superlattice, where each well produces a separate peak. The sample …

Change in dimensionality of superlattice excitons induced by an electric field

We have observed an electric-field-induced change in the dimensionality of excitons in superlattices, from three to quasi-two dimensions. The exciton binding energy of a (40 Å/(40 Å) GaAs/(GaAl)As superlattice, determined from low-temperature …

Coherence and localization in semiconductor superlattices under electric fields

Using optical techniques, we have demonstrated that the quantum coherence of electron states in GaAs/GaAlAs superlattices under electric fields increases drastically as the period, $D$, and the electric field, $\cal{E}$, decrease, reaching at least …

Interactions between extended and localized states in superlattices

We have observed electric-field-induced interactions between the extended states of a (40 Å)-(15 Å) GaAs-Ga0.65Al0.35As superlattice and the localized state of an 80-Å terminating GaAs well. At fields such that the energy of an extended state was …