photocurrent

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 …

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 …

Temperature Dependence of the Electronic Coherence of GaAs-GaAlAs Superlattices

We have shown that the coherence length of electrons in a 55-Å-period GaAs-GaAlAs superlattice does not depend strongly on temperature in the range 5--292 K, varying from 17 periods at 5 K to a minimum of nine periods at room temperature. The quantum …

Optical properties of quantum wells and superlattices under electric fields

We review the effects of a longitudinal electric field on the optical properties of semiconductor quantum wells and superlattices, emphasizing recent developments on the latter, such as the observation of the Stark ladder, field-induced localization, …

Quantum coherence in semiconductor superlattices

Using photocurrent spectroscopy, we have demonstrated that the quantum coherence in GaAs-Ga$_{1-x}$Al$_x$As superlattices increases with decreasing superlattice period $D$, and that it is maintained for at least eight periods when $D = 60$ Å. The …

Stark Localization in GaAs-GaAlAs Superlattices under an Electric Field

We have observed that a strong electric field $\cal E$ shifts to higher energies the photoluminescence and photocurrent peaks of a GaAs-Ga$_{0.65}$Al$_{0.35}$As superlattice of period $D$ (=65 Å), which we explain by a field-induced localization of …