Limiting factors to the performance and operation frequency range of THz quantum cascade laser based on GaAs/AlGaAs heterostructures

We have designed and fabricated 2.3 THz QCL with active module based on 4 QWs GaAs/Al0.15Ga0.85As. The light-current-voltage (L-I-V) characteristics and emission spectra of fabricated THz QCL are investigated. The nonmonotonic behavior of L–I characteristic and a large number of discontinuities in I-V characteristic is observed. Our calculations show that such electric instabilities are associated with the field inhomogeneity across the active region (electric field domains). We investigate transmission spectra of incident radiation of GaAs and AlGaAs/GaAs structures with two highly absorption optical response regions. Thus, to improve the performance and extend the operation frequencies of THz QCLs it is needed to develop new concepts of active region designs for avoiding the formation of electric field domains and employ novel material systems for lasing in the frequency range 8-11 THz.