Thursday, August 25, 2016
Abstract-Room temperature negative differential resistance in terahertz quantum cascade laser structures
The mechanisms that limit the performance of GaAs/AlGaAs-based terahertz (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved performance. Here, we study the performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher levels, rather than the escape into the continuum. Based on this understanding, we have designed a structure with an increased intersubband spacing between the upper lasing level and in a highly diagonal THz-QCL, which exhibits even at room This result is a strong evidence for the effective suppression of the aforementioned leakage channel.