Silicon carbide (SiC), a material long known with potential for high-temperature, high-power, high-frequency, and radiation hardened applications, has emerged as the most mature of the wide-bandgap (2.0 eV ≲ Eg ≲ 7.0 eV) semiconductors since the release of commercial 6HSiC bulk substrates in 1991 and 4HSiC substrates in 1994. Following a brief introduction to SiC material properties, the status of SiC in terms of bulk crystal growth, unit device fabrication processes, device performance, circuits and sensors is discussed. Emphasis is placed upon demonstrated high-temperature applications, such as power transistors and rectifiers, turbine engine combustion monitoring, temperature sensors, analog and digital circuitry, flame detectors, and accelerometers. While individual device performances have been impressive (e.g. 4HSiC MESFETs with fmax of 42 GHz and over 2.8 W mm−1 power density; 4HSiC static induction transistors with 225 W power output at 600 MHz, 47% power added efficiency (PAE), and 200 V forward blocking voltage), material defects in SiC, in particular micropipe defects, remain the primary impediment to wide-spread application in commercial markets. Micropipe defect densities have been reduced from near the 1000 cm−2 order of magnitude in 1992 to 3.5 cm−2 at the research level in 1995.

Status of silicon carbide (SiC) as a wide-bandgap semiconductor for high-temperature applications: A review

Silicon offers multiple advantages to power circuit designers, but at the same time suffers from limitations that are inherent to silicon material properties, such as low bandgap energy, low thermal conductivity, and switching frequency limitations. Wide bandgap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), provide larger bandgaps, higher breakdown electric field, and higher thermal conductivity. Power semiconductor devices made with SiC and GaN are capable of higher blocking voltages, higher switching frequencies, and higher junction temperatures than silicon devices. SiC is by far the most advanced material and, hence, is the subject of attention from power electronics and systems designers. This paper looks at the benefits of using SiC in power electronics applications, reviews the current state of the art, and shows how SiC can be a strong and viable candidate for future power electronics and systems applications.

Silicon carbide benefits and advantages for power electronics circuits and systems

SiC electronic device technology has made rapid progress during the past decade In this paper, we review the evolution of SiC power MOSFETs between 1992 and the present, discuss the current status of device development, identify the critical fabrication issues, and assess the prospects for continued progress and eventual commercialization

Status and prospects for SiC power MOSFETs

In recent years, silicon carbide has received increased attention because of its potential for high-power devices. The unique material properties of SiC, high electric breakdown field, high saturated electron drift velocity, and high thermal conductivity are what give this material its tremendous potential in the power device arena. 4H-SiC Schottky barrier diodes (1400 V) with forward current densities over 700 A/cm/sup 2/ at 2 V have been demonstrated. Packaged SITs have produced 57 W of output power at 500 MHz, SiC UMOSFETs (1200 V) are projected to have 15 times the current density of Si IGBTs (1200 V). Submicron gate length 4H-SiC MESFETs have achieved f/sub max/=32 GHz, f/sub T/=14.0 GHz, and power density=2.8 W/mm @ 1.8 GHz. The performances of a wide variety of SiC devices are compared to that of similar Si and GaAs devices and to theoretically expected results.

Silicon carbide high-power devices

A sustainable energy future requires power electronics that can enable significantly higher efficiencies in the generation, distribution, and usage of electrical energy. Silicon carbide (4H-SiC) is one of the most technologically advanced wide bandgap semiconductor that can outperform conventional silicon in terms of power handling, maximum operating temperature, and power conversion efficiency in power modules. While SiC Schottky diode is a mature technology, SiC power Metal Oxide Semiconductor Field Effect Transistors are relatively novel and there is large room for performance improvement. Specifically, major initiatives are under way to improve the inversion channel mobility and gate oxide stability in order to further reduce the on-resistance and enhance the gate reliability. Both problems relate to the defects near the SiO2/SiC interface, which have been the focus of intensive studies for more than a decade. Here we review research on the SiC MOS physics and technology, including its brief history, the state-of-art, and the latest progress in this field. We focus on the two main scientific problems, namely, low channel mobility and bias temperature instability. The possible mechanisms behind these issues are discussed at the device physics level as well as the atomic scale, with the support of published physical analysis and theoretical studies results. Some of the most exciting recent progress in interface engineering for improving the channel mobility and fundamental understanding of channel transport is reviewed.

Silicon carbide: A unique platform for metal-oxide-semiconductor physics

MESFET's were fabricated using 4H-SiC substrates and epitaxy The DC, S-parameter, and output power characteristics of the 07 /spl mu/m gate length, 332 /spl mu/m gate width MESFET's were measured At /spl nu//sub ds/=25 V the current density was about 300 mA/mm and the maximum transconductance was in the range of 38-42 mS/mm The device had 93 dB gain at 5 GHz and f/sub max/=129 GHz At V/sub ds/=54 V the power density was 28 W/mm with a power added efficiency=127% >

4H-SiC MESFET with 2.8 W/mm power density at 1.8 GHz

4H-SiC MESFET's on conducting substrates were fabricated and characterized for large-signal performance over a wide range of gate and drain biases. At V/sub ds/=25 V the current density was 225 mA/mm and the peak f/sub max/ for these devices was 16 GHz. At V/sub ds/=50 V and I/sub dq/=50% I/sub dss/, the power density was 3.3 W/mm at 850 MHz. At V/sub ds/=40 V and I/sub dq/=5% I/sub dss/, the power added efficiency was 65.7%, which is the highest ever reported for a SiC MESFET. This is the first Class B data presented for a SiC MESFET.

4H-SiC MESFET with 65.7% power added efficiency at 850 MHz

Realization of the full potential of semiconductor SiC for electronic and optical applications is critically dependent on the production of large diameter SiC single-crystals of high crystalline quality and controlled impurity content as well as high quality uniform epitaxial layers. In this paper, current substrate and epitaxial issues are presented in the light of recent results. Progress in monocrystalline SiC bulk crystal growth is characterized by the attainment of substrate diameters up to 100-mm; residual impurities in the 10/sup 15/ cm/sup -3/ range; and micropipe densities as low as 1.1 cm/sup -2/ over an entire 50-mm diameter 4H-SiC wafer. Epitaxial growth progress is highlighted by growth rates as high as 50 /spl mu/m/h, residual impurities of 10/sup 14/ cm/sup -3/, and doping uniformities of less than 4.7% in commercial multiwafer reactors. Current materials challenges are the reduction of micropipes, dislocations and dislocation related defects.

C.H. Carter

Papers

Silicon carbide high-power devices

4H-SiC MESFET with 2.8 W/mm power density at 1.8 GHz

4H-SiC MESFET with 65.7% power added efficiency at 850 MHz

Substrate and epitaxial issues for SiC power devices