Temperature dependence of channel mobility in HfO2-gated NMOSFETS

The degradation mechanisms of effective electron channel mobility in HfO2-gated nMOSFETs have been studied by analyzing experimental data at various temperatures from 120 to 320 K. The major finding is that, while significant Coulomb scattering plays an important role in causing the observed mobility degradation, it does not account for all of the degradation; rather, it requires an extra phonon scattering mechanism, beyond that arising from the phonons in the Si substrate, to explain our experimental results. This extra phonon scattering mechanism has been found to exhibit relatively weak temperature dependence, and is attributed to the soft optical phonons in the HfO2 layer.