Temperature performance of terahertz quantum-cascade lasers: experiment versus simulation

We report the electrical and the optical characteristics of 2 THz quantum-cascade lasers with a similar four-well resonant-phonon design. A Monte Carlo simulation, employed to evaluate the temperature performance of the device, indicates that the degradation of material gain with increasing temperature is attributed to the rapid decrease in the lifetime of the upper lasing level and the relatively stable lifetime of the lower lasing level. Because of the broadening effect of the temperature dependent gain profile, our calculations overestimate the peak gain and subsequently overrate the maximum operating temperature. Under a linear approximation condition, the deduced maximum operating temperature is in good agreement with experiment. Both experiment and simulation show that the lasing frequency is insensitive to temperature.