Evaluation of Material Systems for THz Quantum Cascade Laser Active Regions

Abstract

Quantum cascade lasers (QCLs) have been realized in several different material systems. In the mid-infrared, active regions are predominantly based on In0.53Ga0.47As and InAs as quantum well material. Market-ready devices routinely provide continuous-wave operation at room temperature. For their THz counterparts, the situation is less clear. The most common material system for THz QCLs is the inherently lattice-matched combination of GaAs with Al0.15Ga0.85As barriers. Yet, these devices still only reach a maximum operating temperature of 200 K with a lack of progress within the past years. Based on the identification of key parameters, this work reviews material systems for quantum cascade lasers with an emphasis on material and growth-related aspects and the goal to identify promising candidates for future device generations. Similar active regions realized in different material systems allow to estimate the gain per unit thickness, as well as total growth times and relative thickness errors.