Aspects of the internal physics of InGaAs∕InAlAs quantum cascade lasers

Abstract

We report on the results of our simulations of an InGaAs/ InAlAs midinfrared quantum cascade laser ͑QCL͒ designed to operate in continuous wave mode at room temperature ͓Beck et al., Science 295, 301 ͑2002͔͒. Our physical model of the device consists of a self-consistent solution of the subband population rate equations and accounts for all electron-longitudinal-optical phonon and electron-electron scattering rates, as well as an evaluation of the temperature of the nonequilibrium electron distribution. We also consider the role of the doping density and its influence on the electron dynamics. We found that the temperature of the nonequilibrium electron distribution differed significantly from the lattice temperature and that this temperature increased with applied electric field and current density, with coupling constants somewhat larger than analogous GaAs based midinfrared QCLs. Our simulations also reveal physical processes of the device that are not apparent from the experimental measurements, such as the role of electron-electron scattering.

Modelling of electronic transport in Quantum Well Infrared Photodetectors

“…We calculate the electronic current by summing all scattering events that cross the plane separating two periods (see Fig. 2) [16].…”

“…A new type of modelling, based on a fully quantum-mechanical model, was first proposed by Harrison et al [2,4,11,12]. This type of modelling, without parameters based on microscopic quantum description of the scattering from state to state, are very appealing and have proven their efficiency to describe other types of quantum structures like the quantum cascade laser (QCL) [8,16]. The specificity of the QWIP is that the electronic transport is mediated by extended states in the conduction band as opposed to QCLs in which it is mediated by localized states.…”

Intervalley Scattering and the Role of Indirect Band Gap AlAs Barriers: Application to GaAs/AlGaAs Quantum Cascade Lasers

“…Also shown are the X potential profile and the corresponding X-states. We determine the self-consistent scattering rates, accounting for all electron-longitudinal-optical phonon and electronelectron scattering rates as well as an evaluation of the non-equilibrium electron distribution [34,35]. Fig.…”

Enhanced performance of quantum cascade Raman laser

“…1 gives the calculated band profile and squared amplitude of the wavefunctions involved in the 1⅓ periods of the structure under an electric field of 50 kV/cm. The major inelastic scattering mechanism in InGaAs/InAlAs systems is via the electron-LO-phonon interaction [17], and we take into account only this process based on Ferreira and Bastard's approach [18]. In order to evaluate the relevant dipole matrix element calculation, we adopted the formulation described in [19], in which we consider the influence of the valence band part of the wavefunctions.…”