Papers by Author: Konstantin Vasilevskiy

Abstract: We present the improvement of SiO₂/4H-SiC interface quality and high field-effect (FE) mobility (µ_FE) in 4H-SiC MOSFETs. This is achieved by introducing a nitrous oxide (N₂O) plasma in-situ pre-treatment before gate stack formation using plasma enhanced chemical vapour deposition (PECVD) oxide followed by a post deposition anneal (PDA) in diluted N₂O for times ranging from 30 to 120 minutes thereby creating an ultra-thin thermally grown SiO₂ layer at the SiO₂/4H-SiC interface. MOS capacitors with SiO₂ deposited on in-situ pre-treated SiC surfaces had a lower density of interface traps (D_IT) for all PDA durations, compared with devices having untreated PECVD oxides or control devices with 30 nm thermally grown oxide. After PDA for 90 minutes, a minimum D_IT value of 1.2×10¹¹ cm^-2·eV^-1 was measured. A peak µ_FE value reaching 94 cm²/(V·s) was measured in n-channel planar MOSFETs fabricated with PECVD oxide on in-situ pre-treated devices, which significantly exceeds a maximum µ_FE of 6 cm²/(V·s) in control devices.

Abstract: Low field electron mobility in heavily nitrogen doped 4H-SiC epitaxial layers as well as in the regions formed by ion implantation was extracted from Hall and van der Pauw measurements. The measurements were done at room temperature in 4H-SiC samples with carrier concentrations ranged from 2.8×10¹⁸ to 2.3×10¹⁹ cm^-3. Fitting parameters in empirical expression given by Caughey and Thomas for room temperature low field electron mobility depending on carrier concentration in 4H-SiC were extracted.

Abstract: Trenched-implanted-gate 4H–SiC vertical-channel JFET (TI-VJFET) have been fabricated with self-aligned nickel silicide source and gate contacts using a process sequence that greatly reduces process complexity as it includes only four lithography steps. The effect of the channel geometry on the electrical characteristics has been studied by varying its length (0.3 and 1.2μm) and its width (1.5-5μm). The transistors exhibited high current handling capabilities (Direct Current density 330A/cm²). The output current reduces with the increase of the measurements temperature due to the decrease of the electron mobility value. The voltage breakdown exhibits a triode shape, which is typical for a static-induction transistor operation.