Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities

摘要

We calculate the intersubband absorption linewidth in quantum wells (QWs) dueto scattering by interface roughness, LO phonons, LA phonons, alloy disorder,and ionized impurities, and compare it with the transport energy broadeningthat corresponds to the transport relaxation time related to electron mobility.Numerical calculations for GaAs QWs clarify the different contributions of eachindividual scattering mechanism to absorption linewidth and transportbroadening. Interface roughness scattering contributes about an order ofmagnitude more to linewidth than to transport broadening, because thecontribution from the intrasubband scattering in the first excited subband ismuch larger than that in the ground subband. On the other hand, LO phononscattering (at room temperature) and ionized impurity scattering contributemuch less to linewidth than to transport broadening. LA phonon scattering makescomparable contributions to linewidth and transport broadening, and so doesalloy disorder scattering. The combination of these contributions withsignificantly different characteristics makes the absolute values of linewidthand transport broadening very different, and leads to the apparent lack ofcorrelation between them when a parameter, such as temperature or alloycomposition, is changed. Our numerical calculations can quantitatively explainthe previously reported experimental results.