Transient dynamics is a key issue for optically pumped quantum well THz laser

which is analyzed for the first time in this paper based on an ensemble Monte Carlo simulation (EMC). The prototype designed is a 3-level stepped modulation doped GaAs/GaxAl(1-x)As quantum well. In this EMC there are electron-electron (e-e)

electron-optical phonon and electron-acoustic phonon scatterings included

and the electron-ionized impurity scattering can be ignored due to modulation doping. The reported THz prototypes of 3-level stepped quantum well were all based on doping in the deepest quantum well

and inconsistent conclusions were drown about the population inversion. We find that population inversion is found in our designed device prototype with temperature 77K and at certain pumping flux.