R.R. Siergiej

700-V asymmetrical 4H-SiC gate turn-off thyristors (GTO's)

Silicon Carbide (4H-SiC), asymmetrical gate turn-off thyristors (GTOs) were fabricated and tested with respect to forward voltage drop (V/sub F/), forward blocking voltage, and turn-off characteristics. Devices were tested from room temperature to 350/spl deg/C in the dc mode. Forward blocking voltages ranged from 600-800 V at room temperature for the devices tested. V/sub F/ of a typical device at 350/spl deg/C was 4.8 V at a current density of 500 A/cm/sup 2/. Turn-off time was less than 1 /spl mu/s. Although no beveling or advanced edge termination techniques were used, the blocking voltage represented approximately 50% of the theoretical value when tested in an air ambient. Also, four GTO cells were connected in parallel to demonstrate 600-V, 1.4 A (800 A/cm/sup 2/) performance.

A critical look at the performance advantages and limitations of 4H-SiC power UMOSFET structures

A realistic performance projection of 4H-SiC UMOSFET structures based on electric field in the gate insulator consistent with long-term reliability of insulator is provided for the breakdown voltage in the range of 600 to 1500 V. The use of P/sup +/ polysilicon gate leads to higher breakdown voltage as the Fowler Nordheim injection from the gate electrode is reduced. It is concluded that the insulator reliability is the limiting factor and therefore the high temperature operation of these devices may not be practical.

RF performance of SiC MESFET's on high resistivity substrates

State-of-the art SiC MESFETs showing a record high f/sub max/ of 26 GHz and RF gain of 8.5 dB at 10 GHz are described in this paper. These results were obtained by using high-resistivity SiC substrates for the first time to minimize substrate parasitics. The fabrication and characterization of these devices are discussed.<<ETX>>

High power 4H-SiC static induction transistors

Static induction transistors have been demonstrated in 4H-SiC. SiC specific semiconductor processing technologies such as epitaxy, reactive ion etching, and sidewall Schottky gates were employed. Under pulsed power test conditions, 4H-SiC SITs developed a maximum output power of 225 W at 600 MHz, a power added efficiency of 47%, and a gain of 8.7 dB. Maximum channel current was 1 A/cm, and the maximum blocking voltage was 200 V.

The mixed mode 4H-SiC SIT as an S-band microwave power transistor

Summary form only given. For the first time, mixed mode 4H-SiC SIT (Static Induction Transistor) devices have been operated for power generation at S-band frequencies. This paper discusses why the SIT is an excellent choice for microwave power transistors in SiC, the technology for SIT fabrication and packaging, and the performance of the first 3.0 GHz SiC power SITs.

High efficiency operation of 6-H SiC MESFETs at 6 GHz

Summary form only given. SiC MESFETs are very promising candidates for RF power amplification, due to their unique combination of high saturation velocity, high breakdown strength, and high thermal conductivity. In the present work, we demonstrate for the first time high efficiency RF power operation at 6 GHz. We have obtained power output of 35 W, with 45.5% power added efficiency at 6 GHz from a 6-H SiC MESFET operating at a drain bias of 40 V. The gate length and width were 0.5 /spl mu/m and 2 mm respectively. The corresponding power density is 1.75 W/mm and is more than a factor of 3 higher than that obtained normally in GaAs. To our knowledge, these results represent the highest power output, efficiency, and operating frequency reported to date in SiC. The power MESFETs were fabricated on high resistivity SiC substrates grown at Westinghouse. Sintered Ni ohmic contacts, mesa isolation, and channel recessing using RIE were used in device fabrication. Air-bridge source interconnects were used for large periphery devices. The fabrication and characterization of these SiC power MESFETs are presented.

Turn-off characteristics of 1000 V SiC gate-turn-off thyristors

10 A//spl sim/175 V switching has been achieved using SiC GTOs. A 3 A/350 V package demonstrated 130 ns and 55 ns rise and fall times with turn-off losses of 3.2 /spl mu/J. Switching times increased by /spl sim/3/spl times/ at 250/spl deg/C. Devices exhibited a dV/dt limit of 700 V//spl mu/s. MOS-gated turn-off of 2 A/100 V is also demonstrated for the first time using a SiC GTO and Si MOSFET in a hybrid MTO/sup TM/ configuration.

Recent progress in 4H-SiC static induction transistors for high frequency power generation

For the first time, 4H-SiC static induction transistors (SITs) have demonstrated 400 W pulsed L-band (1.3 GHz) performance (16.7 W/cm source periphery). Additionally, air-bridged parts have shown 78 W pulsed S-band (2.9 GHz) performance (15.1 W/cm source periphery), as well as 47 W pulsed S-band (4 GHz) performance, which represents the highest power densities yet reported for microwave SITs. The extraordinarily high power densities observed in SiC SITs derive from the remarkable physical properties of SiC. The high value of breakdown field strength (∼3 MV/cm), the large value of saturated electron velocity (2×10/sup 7/ cm/s), and the metallic-like thermal conductivity (4.9 W/cm·K) synergistically combine to generate the observed high power densities at high frequency.

Low frequency noise in 6H-SiC MOSFET's

The noise spectra for n-channel, depletion-mode MOSFETs fabricated in 6H-SiC material were measured from 1-10/sup 5/ Hz at room temperature. Devices were biased in the linear regime, where the noise spectra was found to be dependent upon the drain-to-source bias current density. At a drain-to-source current of 50 /spl mu/A for MOSFETs with a W/L of 400 /spl mu/m/4 /spl mu/m, the measured drain-to-source noise power spectral density was found to be A/(f/sup /spl lambda//), with A being 2.6/spl times/10/sup -12/ V/sup 2/, and /spl lambda/ being between 0.73 and 0.85, indicating a nonuniform spatial trap density skewed towards the oxide-semiconductor interface. The measured Hooge parameter (/spl alpha//sub H/) was 2/spl times/10/sup -5/. This letter represents the first reported noise characterization of 6H-SiC MOSFETs.

Novel SiC device technology featuring enhancement and depletion mode transistors

Silicon Carbide (SiC) has enjoyed rapid success in discrete device development primarily due to the availability of single crystal wafers and the similarities which exist with present day silicon technologies. Some of the devices which have been fabricated in SiC include the MOSFET, MESFET, thyristor, JFET, and UMOS. Additionally some devices, such as MOSFETs and MESFETs, have been utilized in integrated form to demonstrate digital and analog circuitry. However, the MOS devices used in integrated circuits have all been of one type, either enhancement or depletion. It is the purpose of the present study to investigate an integrated circuit technology which provides both enhancement and depletion mode NMOS transistors. This type of circuit technology is desirable for high-density circuit integration schemes since it consumes less area than an all enhancement or depletion mode design.