Low-Threshold Terahertz Quantum-Cascade Lasers Based On Gaas/Al0.25ga0.75as Heterostructures

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.(C) 2010 American Institute of Physics. [doi:10.1063/1.3480406]