Modelling And Simulation Of Quantum Cascade Lasers

Quantum cascade laser (QCL) is a kind of semiconductor laser which rely on optical transitions between quantized states of the conduction band. It’s invention broke the restraint in traditional semiconductor lasers, and fill the gap in mid-and far infrared spectrum. Because of their excellent performance and important using value, QCLs have made dramatic progress in the past decades. In spite of the dramatic strides made in QCL performance, many applications would benefit from further optimization of device structure. Semiconductor process and device numerical simulation (TC AD) would be an effective tool to help the process. TC AD tool is not only an effective tool to predict the behaviors of new structures and help designers optimize their performances, but also an important way to help us understand the properties of existing structures.A reliable TC AD tool is based on accurate physical models, and an accurate physical model comes from the in-depth study of the physical processes in the device. As a complex quantum system, QCL can be modeled in various ways, from the rate equation model. Monte-Carlo simulations, to the non-equilibrium Green’s function. In this study, with LASTIP(2D semiconductor laser simulation software) provided by Crosslight Software Inc., a comprehensive simulation model for QCL has been improved based on the framework provided by LASTIP. The model has been implanted in the2D simulation software LASTIP and3D simulation software PICS3D.A comprehensive simulation model for QCLs based on the integration of a number of optoelectronic models on both microscopic and macroscopic scales is reported in this thesis. On the microscopic scale, quantum mechanical computation was performed to find the quantization states and a rate equation approach was used to compute the optical gain. On the macroscopic scale, we solved the drift-diffusion equations with modification of current density to account for long-range carrier transport, including quantum tunneling, mini-band tunneling, and hot carrier transport. Multiple lateral optical modes were computed by solving a scalar wave equation as an eigenvalue problem. Finally, multiple lateral mode laser cavity photon rate equations were solved with the drift-diffusion equations in a self-consistent manner to predict the lasing characteristics of a quantum cascade laser.The comprehensive simulation model shown above is verified by two parts of calculations. Firstly based on the simulation of two groups of experimental data from a number of AlInGaAs/InP mid-infrared QCLs, the accuracy of non-local transport model is verified. The original transport model in LASTIP is also improved during this process. A further discussion and study of non-local transport model is give based on a large number of simulations. Secondly, based on the simulation of a classic three-well active region mid-infrared QCL, the accuracy of optical gain model is verified. A complete simulation flow of QCLs in LASTIP is shown here. Finally, some2D simulation results of two groups of QCLs with different structures are shown.