Strain and nonparabolicity effects in Mid-infrared GaxIn1-xAsySb1-y/AlxGayIn1-x-yAszSb1-z MQW QCL

In this paper, we present a theoretical study of strain and nonparabolicity effects in Mid-infrared (MIR) GaxIn1-xAsySb1-y/AlxGayIn1-x-yAszSb1-z Multiple Quantum Well (MQW) Quantum Cascade Lasers (QCL). We use an envelope function k.P theory model to show the strong effects of bi-axial compressive strain and nonparabolicity on conduction band states of the QCL. These effects are shown to result more particularly in an increase of the electron effective mass near the fundamental laser emission energy transition of the QCL. This in turn is found to have a significant influence on several optical properties of the QCL as a reduction of laser transition energy i.e. an increase of the laser emission wavelength, a decrease of the transit time in the injection region of the QCL, a reduction of the optical dipole matrix element, a reduction of the optical gain of the laser.