Self-consistent analysis of carrier transport and carrier capature dynamics in quantum cascade intersubband semiconductor lasers

摘要

The present contribution describes a theoretical framework for performing calculations of the fundamental time constants which determine the dynamics of carrier transport and carrier capature in intersubband quantum cascade semiconductor lasers. In a recent brief report [1] it was indicated that unipolar lasers have the potential for achieving THz modulation bandwidths and a detailed ldescription of that analysis has been presented elsewhere [2]. All that work was concerned with the dynamical processes occurring in a single triple-quantum well element. In practical intersubband lasers, in order to achieve sufficient optical gain, the active region must contain many copies of such elements so as to achieve the quantum cascade effect which underpins the successful operation of this class of lasers. In order to analyse the dynamical porcesses at play in such a quantum cascade laser, attention needs to be given to carrier transport and carrier capature processes which will affect, in particular, the achievable direct current modulation frequency of intersubband cascade lasers. In this report, a theoretical framework will be established to perform calculations of the pertinent physical factors which govern carrier transport.