Comparison of the temperature performance for various record temperature terahertz structures. The horizontal line is set to the gain at 178 K, the solid and dashed curves are corrected for the differences in resonator losses of the structures.
Improved three quantum well designs: Conduction band profile and probability densities of the (a) ID scheme, (b) SB scheme, and (c) merged structure. In the figure plots, the layer sequence is given in Å, where the subscript represents the Al concentration in the Al x Ga1− x As layer. The mid-region of the injector well is doped with a sheet density of .
Simulated temperature dependent peak gain of the structures, showing an improvement in of about 16 K for the ID, 11 K for the SB, and 31 K for their merged design.
Conduction band profile and probability densities for QCLs with the same oscillator strength as for the reference design with (a) two barrier compositions (2BC) and (b) three barrier compositions (3BC). The mid-region of the injector well is doped with a sheet density of . (c) Simulated temperature dependent peak gain, showing an improvement in of about 26 K for the 2BC design and 38 K for the 3BC design as compared to the reference structure.
Summary for the properties of the designed structures at 200 K as compared to the reference design (199.5 K record structure4). The populations for the different levels (, , and ), the injection efficiencies into the upper and lower laser level ( and ), the maximum current density , the total () and main lasing transition oscillator strength and the gain bandwidths (BW) are compared. Precise definitions for can be found in Ref. 53.
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