Carriers In Semiconductor Superlattices Research Articles

Lateral transport of photoexcited carriers in semiconductor superlattices

I investigate the lateral transport of photoexcited carriers in semiconductor superlattices by microphotoluminescence imaging. Tuning the excitation excess energy, I find that the transport length of carriers shows pronounced and regular oscillation feature with a period of about 5 meV. Such a behavior is not observed from quantum-well structure under similar conditions, confirming it as an intrinsic property of carriers in superlattices. A qualitative explanation is proposed based on folding of the Brillouin zone and of the phonon dispersion. The experimental result reveals the complication of lateral transport process and implies a coupling between lateral and vertical transports of carriers in superlattice.

Ultrafast Relaxation of Photoexcited Carriers in Semiconductor Superlattices

The differential transmission signal (DTS) of a pump-probe transmission experiment on the GaAs/AlGaAs superlattice is calculated using the effective semiconductor Bloch equation and by assuming that the main mechanism of the relaxation for a low carrier density is the carrier LO-phonon scattering. From the theoretical analysis of the DTS signal, the intrasubband and intersubband relaxation times of the carriers which are excited optically to the second miniband are estimated. The results are compared to those of recent femtosecond pump-probe experiments on the GaAs/AlGaAs superlattice.

Coherent carrier dynamics in semiconductor superlattices

We investigate the coherent dynamics of carriers in semiconductor superlattices driven by ac-dc electric fields. We solve numerically the time-dependent effective-mass equation for the envelope function. We find that carriers undergo Rabi oscillations when the driving frequency is close to the separation between minibands.

Ultrafast carrier relaxation and vertical-transport phenomena in semiconductor superlattices: A Monte Carlo analysis.

The ultrafast dynamics of photoexcited carriers in semiconductor superlattices is studied theoretically on the basis of a Monte Carlo solution of the coupled Boltzmann transport equations for electrons and holes. The approach allows a kinetic description of the relevant interaction mechanisms such as intra- miniband and interminiband carrier-phonon scattering processes. The energy relaxation of photoexcited carriers, as well as their vertical transport, is investigated in detail. The effects of the multiminiband nature of the superlattice spectrum on the energy relaxation process are discussed with particular emphasis on the presence of Bloch oscillations induced by an external electric field. The analysis is performed for different superlattice structures and excitation conditions. It shows the dominant role of carrier\char21{}polar-optical-phonon interaction in determining the nature of the carrier dynamics in the low-density limit. In particular, the miniband width, compared to the phonon energy, turns out to be a relevant quantity in predicting the existence of Bloch oscillations.

Relaxation and tunneling dynamics of photogenerated carriers in semiconductor superlattices.

Population mixing and time-resolution techniques were applid to study the dynamical carrier processes inGaAs-AlGaAs superlattices under the perpendicular electric field.Competitive nature of ultrafast processes ofphoto-excited electron-hole pairs, exciton formation and pair ionization followed by tunneling through barriers, are clarified under the various electric field.

Optical nonlinearity resulting from mobile carriers in semiconductor superlattices: Influence of higher minibands

We have investigated the temperature dependence of χ(3) optical nonlinearities associated with mobile carriers in a superlattice. Our computer calculations show that at temperatures near 300 K, the population of higher minibands can significantly increase χ(3) over that predicted by considering only the lowest miniband. The magnitude of this increase is strongly correlated with the layer configuration of the superlattice and its associated band structure.