The drift region properties of 6H- and 3C-SiC-based Schottky rectifiers and power MOSFETs that result in breakdown voltages from 50 to 5000 V are defined. Using these values, the output characteristics of the devices are calculated and compared with those of Si devices. It is found that due to very low drift region resistance, 5000-V SiC Schottky rectifiers and power MOSFETs can deliver on-state current density of 100 A/cm/sup 2/ at room temperature with a forward drop of only 3.85 and 2.95 V, respectively. Both devices are expected to have excellent switching characteristics and ruggedness due to the absence of minority-carrier injection. A thermal analysis shows that 5000-V, 6H-, and 3C-SiC MOSFETs and Schottky rectifiers would be approximately 20 and 18 times smaller than corresponding Si devices, and that operation at higher temperatures and at higher breakdown voltages than conventional Si devices is possible. Also, a significant reduction in the die size is expected. >

Comparison of 6H-SiC, 3C-SiC, and Si for power devices

This paper presents a critical evaluation of the performance capabilities of various wide bandgap semiconductors for high power and high frequency unipolar electronic devices. Seven different figures of merit have been analyzed. Theoretical calculations show that besides diamond and SiC, compounds like AlN, GaN, InN, and ZnO, and the intermetallics (Ga/sub x/In/sub 1-x/N, Al/sub x/In/sub 1-x/N, Al/sub x/Ga/sub 1-x/N, and (AlN)/sub x/(SiC)/sub 1-x/) offer several orders of magnitude improvement in the on-resistance and in the potential for successful operation at higher temperatures. >

Wide bandgap compound semiconductors for superior high-voltage unipolar power devices

The important material parameters for 6H silicon carbide (6H-SiC) are extracted from the literature and implemented into the 2-D device simulation programs PISCES and BREAKDOWN and into the 1-D program OSSI Simulations of 6H-SiC p-n junctions show the possibility to operate corresponding devices at temperatures up to 1000 K thanks to their low reverse current densities. Comparison of a 6H-SiC 1200 V p-n/sup -/-n/sup +/ diode with a corresponding silicon (Si) diode shows the higher switching performance of the 6H-SiC diode, while the forward power loss is somewhat higher than in Si due to the higher built-in voltage of the 6H-SiC p-n junction. This disadvantage can be avoided by a 6H-SiC Schottky diode. The on-resistances of Si, 3C-SiC, and 6H-SiC vertical power MOSFET's are compared by analytical calculations. At room temperature, such SiC MOSFET's can operate up to blocking capabilities of 5000 V with an on-resistance below 0.1 /spl Omega/cm/sup 2/, while Si MOSFET's are limited to below 500 V. This is checked by calculating the characteristics of a 6H-SiC 1200 V MOSFET with PISCES. In the voltage region below 200 V, Si is superior due to its higher mobility and lower threshold voltage. Electric fields in the order of 4/spl times/10/sup 6/ V/cm occur in the gate oxide of the mentioned 6H-SiC MOSFET as well as in a field plate oxide used to passivate its planar junction. To investigate the high frequency performance of SiC devices, a heterobipolartransistor with a 6H-SiC emitter is considered. Base and collector are assumed to be out of 3C-SiC. Frequencies up to 10 GHz with a very high output power are obtained on the basis of analytical considerations. >

SiC devices: physics and numerical simulation

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

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

Elemental and compound semiconductors, including wide-bandgap semiconductors, are critically examined for high-power electronic applications in terms of several parameters. On the basis of an analysis applicable to a wide range of semiconducting materials and by using the available measured physical parameters, it is shown that wide-bandgap semiconductors such as SiC and diamond could offer significant advantages compared to either silicon or group III-V compound semiconductors for these applications. The analysis uses peak electric field strength at avalanche breakdown as a critical material parameter for evaluating the quality of a semiconducting material for high-power electronics. Theoretical calculations show improvement by orders of magnitude in the on-resistance, twentyfold improvement in the maximum frequency of operation, and potential for successful operation at temperatures beyond 600 degrees C for diamond high-power devices. New figures of merit for power-handling capability that emphasize electrical and thermal conductivities of the material are derived and are applied to various semiconducting materials. It is shown that an improvement in power-handling capabilities of semiconductor devices by three orders of magnitude is feasible by replacing silicon with silicon carbide; improvement in power-handling capability by six orders of magnitude is projected for diamond-based devices. >

Optimum semiconductors for high-power electronics

Based on a new analysis which uses the peak electric field strength at avalanche breakdown as the critical material parameter it is shown that wide bandgap semiconductors are by far the most desirable materials for high-power electronic applications. The specific materials investigated include the elemental semiconductors such as silicon and germanium, compound semiconductors such as GaAs and GaP, and the emerging wide bandgap semiconductors such as SiC and diamond. The fundamental material parameters are related to important device parameters for high-temperature, high-frequency, and high-power electronic applications. New figures of merit for power-handling capabilities that emphasize electrical and thermal conductivities of the materials are derived and applied to various semiconductors. It is shown that improvement in power-handling capabilities of semiconductor devices by three orders of magnitude is feasible by replacing silicon with silicon carbide; improvement in power-handling capability by six orders of magnitude is projected for diamond-based devices.

R. S. Scott

Papers

Optimum semiconductors for high-power electronics

New Material and Device Design Considerations for High-Power Electronics