Spectroscopic line shape broadening mechanisms in PbSe/PbSrSe quantum wells

Temperature-dependent infrared transmission measurements on molecular-beam-epitaxy-grown PbSe/Pb0.934Sr0.066Se multiple-quantum-well structures (MQWs) have been carried out for the study of line shape broadening mechanisms. The longitudinal–optical phonon scattering strength is found to be much smaller in PbSe/Pb0.934Sr0.066Se MQWs (∼11–12 meV) than that in the corresponding IV–VI films (∼51 meV), which is in good agreement with the theoretical prediction. The low-temperature transmission line shapes of PbSe/Pb0.934Sr0.066Se MQWs are analyzed on the basis of the modeling of three broadening mechanisms. For the transmission spectra, the line shape broadening is mainly due to the well width fluctuation for quantum wells thinner than 15 nm and due to the interface roughness for quantum wells thicker than 15 nm. However, the line shape broadening due to the sheet carrier density in PbSe wells has been found to play a dominant role in the photoluminescence linewidth.