On the suppression of phonon-electron scattering in short periodic AlAs/GaAs multiple quantum well structures

The suppression of longitudinal optical phonon (LOP)-electron scattering was sought in multiple quantum well (MQW) structures. The structures had GaAs well widths=12, 15 and 20 mono layers (ML) and AlAs barrier widths =2 and 4 ML. The MQWs were grown in the channel of GaAs/Al_0.3Ga_0.7As modulation doped field effect transistors (MODFETs) without gates. The Hall mobility and carrier sheet density were measured by the van der Pauw method. The Hall mobility of the MQW samples was found to be less than that of the control samples (without MQW) at room temperature, but was better at temperatures lower than 50 K. The reduction of the room temperature mobility was due to interaction of the well electrons with the interface polaritons from the AlAs barriers. The increase of the low temperature mobility was due to reduced remote ionized impurity scattering of the well electrons. The evidence of performance improvement of MQW devices at room temperature due to suppression of electron-LOP scattering is thus disputed by this study. The results of an experiment made elsewhere, which appeared to show the contrary, can be interpreted using arguments other than the suppression of electron-LOP scattering in MQWs