Improved Electrical Characteristics of Gallium Oxide/P-Epi Silicon Carbide Static Induction Transistors with UV/Ozone Treatment Fabricated by RF Sputter

In this study, static induction transistors (SITs) with beta gallium oxide (β-Ga2O3) channels are grown on a p-epi silicon carbide (SiC) layer via radio frequency sputtering. The Ga2O3 films are subjected to UV/ozone treatment, which results in reduced oxygen vacancies in the X-ray photoelectron spectroscopy data, lower surface roughness (3.51 nm) and resistivity (319 Ω·cm), and higher mobility (4.01 cm2V−1s−1). The gate leakage current is as low as 1.0 × 10−11 A at VGS = 10 V by the depletion layer formed between n-Ga2O3 and p-epi SiC at the gate region with a PN heterojunction. The UV/O3-treated SITs exhibit higher (approximately 1.64 × 102 times) drain current (VDS = 12 V) and on/off ratio (4.32 × 105) than non-treated control devices.

Effect of Nitrogen Gas Plasma Generated by a Fast-Pulsed Power Supply Using a Static Induction Thyristor on Scrapie Prion

Previous studies show that nitrogen gas plasma generated by a fast-pulsed power supply using a static induction thyristor has both virucidal and bactericidal effects. In this study, nitrogen gas plasma was further evaluated for its potential effects on prions, which are well known to be the most resistant pathogen to both chemical and physical inactivation. Aliquots (10 μL) of mouse brain homogenate infected with Chandler scrapie prion were spotted onto cover glasses and subjected to nitrogen gas plasma. Treated samples were recovered and subjected to further analyses. Control prion samples were prepared in exactly the same way but without plasma treatment. Protein misfolding cyclic amplification (PMCA) showed that nitrogen gas plasma treatment at 1.5 kilo pulse per second for 15 or 30 min caused a reduction in the in vitro propagation level of PrPres (proteinase K-resistant prion protein), which was used as an index of abnormal prion protein (PrPSc). Moreover, mice injected with prion treated with plasma for 30 min showed longer survival than mice injected with control prion, indicating that nitrogen gas plasma treatment decreased prion infectivity. Altogether, these results suggest that nitrogen gas plasma treatment can inactivate scrapie prions by decreasing the propagation activity and infectivity of PrPSc.

Stress Test of Cascode Switch Using SiC Static Induction Transistor

Stress tests were conducted for the cascode switch using the SiC buried gate static induction transistor (SiC-BGSIT). The stress of the reverse overshoot voltage was periodically applied to the pn junction between the gate terminal and source one in the BGSIT in the cascode with pulses of 40kHz for 202 hours. This simulates the stress which can be occurred in the channel region of the BGSIT during the turn-off and turn-on operation with a parasitic inductance in the interconnection of the cascode package. The result of the stress tests has revealed that there is no significant difference between the electrical characteristics of the BGSIT cascode sample before the stress and those after the stress. Thus, the BGSIT cascode can guarantee high reliability against the stress. The result from the drain current DLTS suggests that no deferent kind of defect is created in the channel region of the BGSIT by the stress.