Silicon-based injection lasers using electronic intersubband transitions in the L valleys

The authors investigate the use of electronic intersubband transitions in Ge∕SiGe quantum wells on SiGe (001) virtual substrates for the development of silicon-based long-wavelength quantum cascade lasers. These heterostructures can provide relatively strong quantum confinement in the Ge L valleys particularly if the SiGe layers are sufficiently thin so that L-to-Δ intervalley scattering paths are suppressed. Numerical simulations indicate that low-threshold operation can be obtained from these devices, thanks to the nonpolar nature of SiGe. Furthermore, the tensor properties of the L-valley effective mass are favorable for the development of vertical emitting intersubband lasers.