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A significant enhancement in the output power of a GaAs-based terahertz quantum cascade laser (THz QCL) was achieved by implementing a relatively high impurity doping concentration. The QC structure was precisely designed using the nonequilibrium green function method by considering the band bending effect caused by a higher doping concentration. This enabled us to avoid the subband misalignment induced by the strong band bending effect, to provide efficient carrier transport even at high doping concentrations, and to improve the output power. The maximum output power of a GaAs/Al0.16Ga0.84As 3.5 THz-band QCL at 10 K was enhanced from 390 to 600 mW by increasing the doping concentration at the depopulation layers from 6 × 1016 to 1.2 × 1017 cm−3. The average power of 21 mW was achieved by implementing the appropriate pulse drive conditions. [ABSTRACT FROM AUTHOR]

A GaAs/AlGaAs‐based terahertz quantum cascade laser with a peak power of 1.31 W and average power of 52 mW is demonstrated. To realize a high output power, an effective way is to increase the electron density at the active region by using a high doping level. This work aims to optimize a design enabling to use a heavy doping level, by realigning the resonant tunneling which can be seriously degraded due to a band bending from this heavy local doping. With variable quantum well and barrier height, the design owns an improved parameter tuning freedoms, and a saturation of peak gain can be achieved at a relatively high doping concentration of 1.0 × 1017 cm−3, which is twice higher than the recently reported device. Nonequilibrium Green's function method including full carriers scattering effect is used to carry out the design optimization, mainly including the realignment of resonant tunneling and suppression of leakages via high‐energy confined levels. In the experiment, a 14 μm thick active layer for this design is grown and also large mesa size is developed. To ensure a quasi‐continuous wave (quasi‐CW) operation, the heat dissipation is also managed. [ABSTRACT FROM AUTHOR]