γ~3 μm GaAs-based active region of quantum cascade laser

The design of an active region of In_xGa_1-xAs_1-yN_y/AlAs quantum cascade laser structure emitting near the 3 μm wavelength based on the ten-band k·p model was reported. The In_xGa_1-xAs_1-yN_y/AlAs heterostructure system is of significant interest for the development of short wavelength quantum cascade lasers due to its large conduction band discontinuity (~1.5 eV) and compatibility with the mature GaAs fabrication process. From the calculations on the energy dispersions and wave functions of the respective states, it is found that when the conduction band offset is very large so that the first excited state lies above the localized nitrogen level, each of the ground and the first excited states is split into two levels. This effect causes the upper lasing level rising so that the lasing wavelength will be shortened. Finally, an optimized combination of In_0.2Ga_0.8As_0.99N_0.01/ AlAs three-coupled-well structure was obtained. Under an applied field of 65 kV/cm and at room temperature, a shortest laser emission wavelength of 3 μm can be achieved.