Variable Barrier Height AlGaAs/GaAs Quantum Cascade Laser Operating at 3.7 THz.

THz (QCLs) are promising large output power semiconductor‐based THz sources with narrow bandwidths and wide operating frequency ranges. However, the operating temperature of THz QCLs is still limited by the design of its active region. Matyas et al. (2012) theoretically predicted that AlGaAs/GaAs THz QCLs with higher optical gain could be obtained by introducing a variable barrier height structure (Matyas et al., <italic>J. Appl. Phys</italic>. <bold>2012</bold>, <italic>111</italic>, 103106). Based on the proposed variable barrier QC structure, we fabricate AlGaAs/GaAs three‐well type THz QCLs with an additional very thin second extraction barrier and a low barrier height emission barrier. With this device, we obtain lasing operation at 3.7 THz at a maximum operating temperature of 145 K. [ABSTRACT FROM AUTHOR]