Low-threshold terahertz quantum-cascade lasers based on GaAs/Al0.25Ga0.75As heterostructures

Abstract

We investigated the influence of the barrier composition on the performance of GaAs-based terahertz (THz) quantum-cascade lasers (QCLs). Based on a nine-quantum-well active region design for 3–4 THz emission, QCLs with an Al content of x=0.15 and x=0.25 in the AlxGa1−xAs barriers are compared. We found a significantly reduced threshold current density for QCLs with x=0.25 as compared to QCLs with x=0.15, which is due to a weaker coupling of the subband states. The maximum output power and operating temperature of such lasers are reduced due to the onset of negative differential resistance.