Design and simulation of a THz QCL based on image–image depopulation mechanism

We propose and simulate a novel terahertz QCL design based on a new depopulation mechanism which relies on resonant Γ–X electron transfer. The ultrafast scattering rates between Γ- and X-valley states is used to depopulate the lower laser level in a modified GaAs/AlGaAs THz QCL structure. The new QCL design is realised by increasing the Al content of the collection barrier to bring a confined X-state in resonance with the lower laser level. Our results show that under such conditions population inversion can be achieved between the two lasing states. Furthermore, the new design may achieve improved temperature operation compared to existing designs.