Intersubband lasing lifetimes of SiGe/Si and GaAs/AlGaAs multiple quantum well structures

The absence of strong polar optical scattering in silicon-based materials resulting in significantly longer lifetimes than in the III-V semiconductors was emphasized. It was also demonstrated that with only nonpolar optical phonon and acoustic phonon scattering operatives, the lifetimes also did not exhibit the sharp reduction when the laser transition energy surpassed the optical phonon threshold energy. Both Ge_xSi_1-x/Si and GaAs/Al_yGa_1-yAs superlattices were taken into consideration. Theoretical proof that the SiGe/Si system had a great advantage over GaAs/AlGaAs quantum well systems for infrared intersubband lasers was reported. For the same laser frequency, the laser lifetime difference in Ge_0.25Si_0.75/Si was at least an order of magnitude greater than that of Al_0.3Ga_0.7As/GaAs for laser emission energies below and above the optical phonon energy.