Characterization of Effective Mobility and Its Degradation Mechanism in MoS 2 MOSFETs

Effective mobility in top-gated MoS 2 metal-oxide-semiconductor field-effect transistors (MOSFETs) with HfO 2 /TaN gates was investigated. We propose a model for effective mobility in MoS 2 MOSFETs and discuss its usefulness. Parameter fitting of the proposed effective mobility model makes possible a discussion of how the scattering mechanism limits the effective mobility. Charged impurities, phonons, and surface roughness were presumed to be possible causes of scattering, and the effect of contact resistance was also taken into account. In the device exhibiting the better mobility of 17.4 cm 2 /Vs, phonon-assisted hopping carrier transport probably limited the mobility. In contrast, in the device exhibiting the worse mobility of 2.8 cm 2 /Vs, scattering caused by charged impurities dominated the transport characteristics. The proposed model facilitates device-to-device comparisons of carrier transport characteristics of MoS 2 transistors at room temperature and accelerates their further development.