A SiC avalanche breakdown diode (ABD) having a nominal 1-kV breakdown voltage was fabricated to provide improved suppression of voltage transients induced during hard-switched turn-off of solid-state devices. Three SiC ABDs were pulsed 1000 times in an inductive load circuit at peak currents of over 100 A. Superior performance in peak pulse current, clamping voltage, and peak pulse power was seen, compared to the results of two series-connected commercial TVS devices, collectively having a comparable breakdown voltage. The transient thermal response of the SiC ABDs was calculated using a model for energy dissipation in short pulses. SiC ABD design parameters and test data were used to show that the reported performance of these devices was not related to package thermal impedance.

Rapidly improving 4 H-SiC material quality and a maturing MOS process/design have enabled the development of the largest 10 kV MOSFET to date and the first 10 kV n-IGBT capable of flowing 10 A and 4 A, respectively, with very low on- resistances. With 20 V on the gate, both devices have aVp~ 5V with a positive temperature coefficient for on-resistance that facilitates their use in a parallel configuration. Each device has its own advantages. The conductivity modulated n-IGBT offers higher current density operation (up to 100 A/cm ) while the majority carrier MOSFET offers extremely fast 5 kV switching with only 140 nsec of turn-off time and a manageable 160 W/cm of dissipated power at 20 kHz. These exciting results indicate that the 10 kV SiC NMOS switches may potentially revolutionize emerging high voltage, high frequency power electronics.

Heavily doped p-type layers obtained by implanting aluminum near its solubility limit (∼2×1020Al∕cm3) in 4H-SiC are characterized as a function of the implant and anneal temperatures. For a typical implant temperature of 650°C, Al activation rates of ∼6%–35% are obtained for anneals from 1600 to 1750°C, respectively. For higher temperature implants at 1000°C, the Al activation rates are significantly improved, approaching ∼100% for the same anneal temperatures, with a best p-type resistivity of ∼0.20Ωcm. For SiC device fabrication, these results demonstrate that by using higher Al implant temperatures, lower anneal temperatures can be used while obtaining close to 100% Al activation.

Various design issues pertaining to SiC-based IGBTs are described. A trench gate, p-channel IGBT was considered the most appropriate structure for fabrication in SiC. The fabrication and characterization of high temperature SiC IGBTs with high current levels are presented. Using optimized emitter processing, 6H-SiC p-IGBTs show a higher current capability than 4H-SiC p-IGBTs because of their lower emitter contact resistance and higher MOS channel mobility. Since IGBTs rely on minority carrier injection, the low bulk mobility parallel to the c-axis in 6H-SiC was not found to severely affect the current carrying capability as compared with 4H-SiC IGBTs in the present design. Measured results of these devices are described from room temperature to the 350-400/spl deg/C temperature range. For both polytypes, the current capability was found to be much larger when their MOS gates were fabricated in the 112~0 crystal direction compared with the 1100 crystal direction. The emitter (p-type) contact anneal was also found to significantly affect the performance of SiC IGBTs. 4H-SiC IGBTs showed a -85 V blocking capability (room temperature) and on-current of 100 mA at 350/spl deg/C. 6H-SiC IGBTs were demonstrated with -400 V blocking capability (at 25/spl deg/C) and 2 A at 400/spl deg/C.

Planar 4H-SiC accumulation channel field-effect transistor (ACCUFET) have been designed, fabricated, and characterized. Detailed design and processing experiments were conducted on relatively large area ACCUFETs to boost their power ratings. A detailed two-dimensional (2-D) simulation design suggests that the. optimum spacing between two. adjacent P+ regions is approximately 4 mum. A-novel process with epitaxial regrowth over ion implanteIt p+ base region was developed to achieve a high accumulation layer mobility. Process splits from, e nitrogen-rich post gate oxidation anneals revealed that the lowest on-resistance and optimum threshold voltage were obtained from N2O annealed samples. 550 V blocking voltage with 22 mOmega-cm(2), were demonstrated on 2 A 4H-SiC-ACCUFETs. Using a newly developed hex-gate design, larger, 20 A 4H-SiC ACCUFETs are presented here with stable high temperature characteristics. In, these high-current devices, the threshold voltage decreases linearly from 1.5 V to 0.9 V, while the extracted channel mobility increases from 18 cm(2)/V-s to 33.6 cm(2)/V-s as the operating temperature is increased from 30 degreesC to 200 degreesC.

Planar gate 4H-SiC ACCUFETs have been designed, fabricated and characterised, and the highest reported current (> 20 A) for this type of device was achieved. A novel channel design to maximise the channel density was implemented. A low specific on-resistance of 15 mOmega-cm(2) was obtained on a 9 mm(2) device using newly developed N2O anneals on gate oxides. The threshold voltage decreases from 1.5 to 0.9 V, and the extracted channel mobility increases from 18 to 33.6 cm(2)/V-s as the operating temperature is increased from 30 to 200degreesC.

The design, fabrication process, and high temperature characteristics of a 4H-SiC rectifier with a 7.4 kV, 330 A (pulsed) capability is reported. A highly-doped p-type epitaxial anode layer and junction termination extension were used to obtain good on-state and stable reverse blocking characteristics. A forward voltage drop of 4.5 V was observed at 100 A/cm(2) (36 A). Measurements in the 25-200degreesC range show little change in reverse leakage characteristics up to 4.5 kV. Reverse recovery measurements for a forward current density of 100 A/cm(2) show a modest 33% increase (from 18 to 24 A) in the peak reverse recovery current, and only a 113% increase (from 1.8 to 3.8 muC) in Q(pi) at 200degreesC compared to 25degreesC.

This paper reports the detailed design, fabrication, and characterization of two sets of high-power 4H-silicon carbide (4H-SiC) junction barrier Schottky (JBS) diodes - one with a 1500-V, 4-A capability and another with 1410-V, 20-A capability. Two-dimensional (2-D) device simulations show that a grid spacing of 4 /spl mu/m results in the most optimum trade-off between the on-state and off-state characteristics for these device ratings. JBS diodes with linear and honeycombed p/sup +/ grids, Schottky diodes and implanted p-i-n diodes fabricated alongside show that while 4H-SiC JBS diodes behave similar to,Schottky diodes in the on-state and switching characteristics, they show reverse characteristics similar to p-i-n diodes. Measurements on 4H-SiC JBS diodes indicate that the reverse-recovery time (/spl tau//sub rr/) and associated losses are near-zero even at a high reverse dI/dt of 75 A//spl mu/s. A dc/dc converter efficiency improvement of 3-6% was obtained over the fastest, lower blocking voltage silicon (Si) diode when operated in the 100-200 kHz range.

This paper reports the design, fabrication and high temperature characteristics of 1 mm(2), 4 mm(2) and 9 mm(2). 4H-SiC p-i-n rectifiers with 6 kV, 5 kV, and 10 kV blocking voltage, respectively. These results were obtained from two lots in an effort to increase the total power levels on such rectifiers. An innovative design utilizing a highly doped p-type epitaxial Anode layer and junction termination extension (JTE) were used in order to realize good on-state as well as stable blocking characteristics. For the 1 mm(2) and 4 mm(2) rectifier, a forward voltage drop of less"than 5 V was observed at 500 A/cm(2) and the peak reverse recovery current shows a modest 50% increase in the 25 degreesC to 225 degreesC temperature range. On the 10 kV, 9 mm(2) rectifier, a forward voltage drop of less than 4.8 V was observed at 100 A/cm(2) in the entire 25 degreesC to 200 degreesC temperature range. For this device, the reverse recovery characteristics show a modest 110% increase in the peak reverse recovery current from 25 degreesC to 200 degreesC. A dramatically low Q(rr) Of 3.8 muC was obtained at a forward current density of 220 A/cm(2) at 200 degreesC for this ultra high voltage rectifier. These devices show that more than three orders of magnitude reduction in reverse recovery charge is obtained in 4H-SiC rectifiers as compared to comparable Si rectifiers.

Silicon carbide avalanche breakdown diodes (ABDs) were fabricated with different P implant depths, drift layer thicknesses, and doping concentrations. ABDs from 4 different designs, having breakdown voltages near 1 kV, were pulse tested in an inductive load circuit at peak powers of over 110 kW. Total pulsed-energy dissipation was kept nearly the same among the ABDs for a defined pulse subinterval. Results of the pulsed-current tests are presented and conclusions are drawn from comparisons of the ABD clamping voltages about which design provides the highest pulsed-energy capability.