Relaxation mechanisms of the photoelectrons in the second miniband of a superlattice structure

Photoelectron relaxation in the second miniband of a superlattice was studied with a high-pass energy filter at one end of the superlattice. By analyzing the spectral responses with different biases across the energy filter, the photoelectron distribution and relaxation in the second miniband of the superlattice can be resolved. In this paper, a model based on the rate equation is proposed to extract the related parameters of the photoelectron transport. The photoelectrons suffer from both intraminiband and interminiband relaxation. The extracted interminiband relaxation time is 11 ps, while the intraminiband one is in the subpicosecond range. In addition, this structure can also be utilized as an infrared photodetector. Our analysis shows that the fast intraminiband relaxation is the dominant mechanism of the maximum achievable responsivity of the detector and the theoretical model not only provides the insight of the photoelectron transport in the superlattice miniband but also is useful for designing a superlattice infrared photodetector.