Reliable evaluation method for interface state density and effective channel mobility in lateral 4H-SiC MOSFETs

The electrical performance of silicon carbide metal-oxide-semiconductor field effect transistors (4H-SiC MOSFETs) are strongly related to the presence of interface states at the silicon dioxide (SiO2)/4H-SiC interface, whose density is much higher than in the Si/SiO2 system. In particular, the charged interface states determine a degradation of the carrier mobility in the channel of the MOSFET with respect to the bulk mobility. A reliable and consistent method for the evaluation of the interface state density (D (it)) and the effective channel mobility (mu (ch)) in these devices is presented in this work. The two quantities are simultaneously extracted by a combined fit of the current-voltage (I-V) and capacitance-voltage (C-V) electrical characteristics collected on a single device. The simultaneous fit of the I-V and C-V characteristics, which can be easily measured on the same device, noticeably improve the reliability of D (it) and mu (ch) estimation. The results obtained at different temperatures indicate an increase of the mu (ch) with T, in agreement with a dominance of the Coulomb scattering effect as the degradation mechanism of the carrier channel mobility induced by the presence of charged interface states.