Significant reduction of threshold current density of GaAs/AlGaAs terahertz quantum cascade lasers by using high-al-content AlGaAs barrier

The temperature dependent of threshold current density (J
_th
) of GaAs/Al
_x
Ga
_1-x
As terahertz quantum cascade lasers (THz QCLs) with different Al barrier composition are studied and reported here. One of the most important issues of the recent THz QCLs is their limited operation temperature. Increasing the Al composition in longitudinal optical (LO) phonon depopulation design THz QCLs tend to reduce J
_th
and improve current dynamic range of lasers, which is expected to increase the maximum operation temperature (T
_max
).