Low-parasitic-capacitance 4H-SiC pMOSFETs were demonstrated for high-frequency CMOS inverters. In these pMOSFETs, device characteristics including parasitic capacitances (gate-source, gate-drain capacitance) were investigated and low parasitic capacitance was achieved by the trench gate structure.

This letter reports on a high-temperature pulsewidth modulation (PWM) integrated circuit microfabricated in 4H-SiC bipolar process technology that features an on-chip integrated ramp generator. The circuit has been characterized and shown to be operational in a wide temperature range from 25 to 500 degrees C. The operating frequency of the PWM varies in the range of 160 to 210 kHz and the duty cycle varies less than 17% over the entire temperature range. The proposed PWM is suggested to efficiently and reliably control power converters in extreme environments.

This paper reports an industry standard monolithic 555-timer circuit designed and fabricated in the in-house silicon carbide (SiC) low-voltage bipolar technology. This paper demonstrates the 555-timer integrated circuits (ICs) characterization in both astable and monostable modes of operation, with a supply voltage of 15 V over the wide temperature range of 25 degrees C-500 degrees C. Nonmonotonic temperature dependence was observed for the 555-timer IC frequency, rise time, fall-time, and power dissipation.

This paper reports an industry standard monolithic 555-timer circuit designed and fabricated in the in-house silicon carbide (SiC) low-voltage bipolar technology. The paper demonstrates the 555-timer ICs characterization in both astable and monostable modes of operation, with a supply voltage of 15 V over the wide temperature range of 25 to 500°C. Nonmonotonictemperature dependence was observed for the 555-timer IC frequency, rise-time, fall-time, and power dissipation.

This letter presents the design, fabrication, and characterization of a 4H-SiC n-p-n bipolar junction transistor as a switch controlling an on-chip integrated p-i-n photodiode. The transistor and photodiode share the same epitaxial layers and topside contacts for each terminal. By connecting the collector of the transistor and the anode of the photodiode, the photo current from the photodiode is switched off at low base voltage (cutoff region of the transistor) and switched on at high base voltage (saturation region of the transistor). The transfer voltage of the circuit decreases as the ambient temperature increases (2 mV/degrees C). Both the on-state and off-state current of the circuit have a positive temperature coefficient and the on/off ratio is >80 at temperature ranged from 25 degrees C to 400 degrees C. It is proposed that the on/off ratio can be increased by similar to 1000 times by adding a light blocking layer on the transistor to reduce light induced off-state current in the circuit.

Digital electronics in SiC find use in high-temperature applications. The objective of this study was to fabricate SiC CMOS without using ion implantation. In this letter, we present a recessed channel CMOS process. Selective doping is achieved by etching epitaxial layers into mesas. A deposited SiO₂-film, post-annealed at lowtemperature and re-oxidized in pyrogenic steam, is used as the gate oxide to produce a conformal gate oxide over the non-planar topography. PMOS, NMOS, inverters, and ring oscillators are characterized at 200 °C. The PMOS requires reduced threshold voltage in order to enable long term reliability. This result demonstrates that it is possible to fabricate SiC CMOS without ion implantation and by low-temperature processing.

Previous studies showed that cobalt silicide can form ohmic contacts to p-type 6H-SiC by directly reacting cobalt with 6H-SiC. Similar results can be achieved on 4H-SiC, given the similarities between the different silicon carbide polytypes. However, previous studies using multilayer deposition of silicon/cobalt on 4H-SiC gave ohmic contacts to n-type. In this study, we investigated the cobalt silicide/4H-SiC system to answer two research questions. Can cobalt contacts be self-aligned to contact holes to 4H-SiC? Are the self-aligned contacts ohmic to n-type, p-type, both or neither? Using x-ray diffraction, it was found that a mixture of silicides (Co₂Si and CoSi) was reliably formed at 800°C using rapid thermal processing. The cobalt silicide mixture becomes ohmic to epitaxially grown n-type (1×10¹⁹cm^-3) if annealed at 1000°C, while it shows rectifying properties to epitaxially grown p-type (1×10¹⁹cm^-3) for all tested anneal temperatures in the range 800–1000°C. The specific contact resistivity (ρ_C) to n-type was 4.3×10^-4 Ω cm². This work opens the possibility to investigate other self-aligned contacts to silicon carbide.

This paper presents functional hightemperature analog circuits in silicon carbide bipolar technology. The circuits will collectively form the analog signal conditioning block for a wireless telemetry system in an extreme environment (above 400 degrees C). The signal conditioningblock is composed of a lowdc gain operational amplifier, a negative voltage charge pump (CP), an RC oscillator, and a voltage regulator. The circuits are tested up to 450 degrees C. The measured open-loop gain for the amplifier at 450 degrees C is 30 dB. The regulator provides approximately 9-V output at 450 degrees C for a fixed load current of up to 18 mA and an applied reference of 4.5 V. The negative voltage CP requires an oscillating signal at its input, which is provided by the RC cross-coupled oscillator. The CP provides about -5 V at 450 degrees C.