Effective Thickness and Composition Analysis of Thin AlAs Barriers in THz QCLs through Experimentally Assisted Method

In this study, we investigate the effective thickness and composition of thin AlAs barriers in terahertz quantum cascade lasers (THz QCLs), addressing deviations caused by atomic intermixing and interface grading. Using a combination of experimental data and Non-Equilibrium Green's Function (NEGF) simulations, we analyze a Split-Well Direct-Phonon (SWDP) QCL design. We find that barriers assumed to be pure AlAs often behave like effective AlGaAs barriers, with altered composition and thickness impacting lasing frequency and performance. Our results emphasize the importance of considering effective barrier compositions, rather than nominal ones, for accurate predictions and optimized QCL performance.