Population dynamics in GaN/AlGaN quantum cascade structure under femtosecond pumping

Basing on the density matrix theory we have developed the theoretical model electron transport in GaN/AlGaN photodetectors including both coherent and incoherent constituents. The lifetimes utilized in the model are computed using Fermi´s Golden Rule approach. The computational efficiency of the model is caused by a series of approximations, the most crucial of which is the thermalization model for electron distribution functions belonging to subbands. Obtained results evidence that depending on the molar fraction of the Al in AlGaN semiconductor alloy the electron transport can be governed by the coherent process or incoherent one basing on the electron-phonon scatterings mainly.