Control of carrier dimensionality in InAs quantum cascade lasers and its effect on laser characteristics

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To investigate the effect of carrier dimensionality on the laser characteristics of InAs quantum cascade lasers (QCLs), we applied the magnetic field in the direction parallel and perpendicular to quantum wells (QWs) layers and measured the emission properties. When the magnetic field in the direction perpendicular to QWs was increased, the threshold current density (J_<th>) was decreased most probably due to the formation of the Landau levels. On the other hand, when the magnetic field parallel to QWs was increased, the enhancement of the slope efficiency was observed whereas J_<th> remained unchanged. Also to study its effect on the characteristics of terahertz (THz) QCLs, we fabricated the GaAs THz QCLs. In addition, we observed the intersubband transitions in ZnO QWs which is expected to improve the temperature characteristics of THz QCLs.