Nonparabolicity effects on transition rates due to confined phonons in GaAs-AlGaAs quantum wells (original) (raw)

Nonparabolicity effects on transition rates due to confined phonons in quantum wells

Brazilian Journal of Physics, 1996

We calculate electron-LO-confined-phonon scattering rates in GaAs-AlGaAs quantum wells considering the influence of nonparabo~city on the energy subbands. We find that the subband nonparabohcity increases the scattering rates significantly for all transitions and that this effect is more pronounced as transitions from higher subbands are involved.

Calculations of the inter-subband scattering rates of electrons in GaAs/AlGaAs quantum wells

Microelectronics Journal, 2003

In this presentation, we report the calculated results on hot electron relaxation through inter-and intra-subband scatterings with LO phonons in quantum well structures. The scattering rates were calculated for electrons excited both in the gamma valley and L valleys. The types of optical phonons adapted in our model are determined based on the dielectric continuum model. We have also studied the dependence of the scatterings on the structure parameters of the quantum well.

Electron scattering by optical phonons in AlxGa1-xAs/GaAs/AlxGa1-xAs quantum wells

Physical Review B, 1997

The scattering of a quasi two-dimensional electron gas by optical phonons in selectively doped Al x Ga 1Ϫx As/GaAs/Al x Ga 1Ϫx As quantum wells is systematically studied in order to determine the effect of phonon confinement. The electron states are calculated solving self-consistently Schrödinger and Poisson equations to obtain an accurate dependence upon the structure parameters and the temperature. We study the way the scattering is affected by the form of the phonons calculating the mobility using three models for the phonons. They are considered: ͑a͒ as three dimensional ͑3D͒, ͑b͒ as a set of confined and interface phonons, and ͑c͒ as the normal modes of the heterostructure. The relaxation times for the electron energy subbands are calculated solving the system of Boltzmann equations. The effect of the temperature and the well width variation is also investigated. The results are in a good agreement with experimental measurements. The agreement is only slightly dependent on the model used for the phonons and becomes best when the effect of the heterostructure on the phonon modes is taken into account. ͓S0163-1829͑97͒07624-8͔

Coupled electron and nonequilibrium optical phonon transport in a GaAs quantum well

Journal of Applied Physics, 1997

The self-consistent Monte Carlo technique has been used to solve coupled nonlinear kinetic equations for electrons and optical phonons confined in a GaAs quantum well. We have studied the influence of nonequilibrium phonons on quasi-two-dimensional electron transport for a lattice temperature of 30 K and for a wide range of applied electric fields. A substantial difference in generation and decay times as well as the confinement inside the GaAs/AlAs heterostructure-bounded active region lead to a significant growth of nonequilibrium optical-phonon population generated by a heated electron gas. We have found that when the phonon generation ͑as well as phonon reabsorption by the quasi-two-dimensional carriers͒ becomes significant, there are substantial effects on transport in the quantum well. We show that for low electron concentrations, the hot optical-phonon distribution reflects the main features of the carrier distribution; indeed, it preserves an average quasi-momentum in the forward ͑opposite to electric field͒ direction. However, hot-phonon feedback to the electron system is found to be not essential in this case. For high electron concentrations, enhanced nonequilibrium optical-phonon reabsorption results in phonon distribution which spreads significantly in the quasi-momentum space and essentially loses the characteristic of the forward-peaked anisotropy. The interactions with the confined electron subsystem typically result in an isotropic phonon distribution. In this case, nonequilibrium optical phonons lead to an increase in the mean electron energy and a reduction in the carrier drift velocity.

Effects of confinement on the electron–phonon interaction in Al0.18Ga0.82As/GaAs quantum wells

Journal of Physics-condensed Matter, 2009

Photoluminescence measurements at different temperatures have been performed to investigate the effects of confinement on the electron-phonon interaction in GaAs/AlGaAs quantum wells (QWs). A series of samples with different well widths in the range from 150 up to 750Å was analyzed. Using a fitting procedure based on the Pässler-p model to describe the temperature dependence of the exciton recombination energy, we determined a fit parameter which is related to the strength of the electron-phonon interaction. On the basis of the behavior of this fit parameter as a function of the well width thickness of the samples investigated, we verified that effects of confinement on the exciton recombination energy are still present in QWs with well widths as large as 450Å. Our findings also show that the electron-phonon interaction is three times stronger in GaAs bulk material than in Al 0.18 Ga 0.82 As/GaAs QWs.

Particle localization and phonon sidebands in GaAs/AlxGa1−xAs multiple quantum wells

Physical Review B, 1992

We use time-resolved spectroscopy of the LO-phonon sidebands to study the in-plane localization of carriers and excitons in undoped GaAs/Al"Ga& "Asmultiple quantum wells at low temperatures. We Snd three distinct populations contributing to the radiative recombination (excluding shallow background impurities): (a) weakly localized excitons, their localization dimension being larger than the exciton Bohr radius, (b) tightly localized excitons, (c) separately localized electrons and holes that decay radiatively on a microsecond time scale. The radiative recombination in undoped multiple quantum wells (MQW's) is due to excitons confined in the wells. In most commonly studied MQW's, the luminescence band is Stokes shifted with respect to its excitation spectrum. This is generally understood to be due to excitons localized in the plane of the QW, either by interface roughness [e.g., in GaAs/Al& "As MQW's (Ref. 1

Influence of interface phonons on intersubband scattering in asymmetric coupled quantum wells

Physical Review B, 1993

A theoretical investigation of intersubband transitions in asymmetric coupled GaAs-Al, Ga& "As quantum wells is presented in order to understand the role of interface phonons on intersubband scattering times estimated from photoluminescence up-conversion. Photoexcited carrier behavior is analyzed in relation to recent measurements and shows time constants for electron relaxation in agreement with experimental data. We show that interface modes are vital to intersubband relaxation in these structures.

Electron-phonon scattering rates in GaAs/AlGaAs 2DEG samples below 0.5 K

Surface Science, 1996

We have studied electron heating in a 2DEG in GaAs/AIGaAs heterojunctions below 0.5 IC The electron temperature was raised above the lattice temperature using Joule heat/n& Weak localiT~tion and the temperature-dependent sample resistance were used as thermometers for the electrons. The electron-phonon energy relaxation rate was found to be proportional to T s. We find that the relaxation rate increases with disorder in the system.