Effects of extraction barrier width on performance of terahertz quantum-cascade lasers

Experimental results are presented on the effects of extraction barrier on the performance of resonant phonon terahertz quantum-cascade lasers. The extraction barrier is varied from 48 to 39 A in an otherwise identical 3.4 THz laser structure. It is found that, when the extraction barrier width decreases from 48 to 39 A, the threshold current density at 10 K increases monotonously from 900 A/cm to 1.4 kA/ cm , and the maximum lasing temperature increases from 95 to 110 K. No optimum extraction barrier width was found for maximum lasing temperature.