Future U.S Army electric motor control applications will require power semiconductor devices that operate for thousands of hours at case temperatures of 150°C and higher. For reliable operation of silicon (Si)-based power electronics, the case temperature must be below 120°C. Because of this temperature limitation of Si, new wide bandgap materials, such as silicon carbide (SiC) are being investigated. We report on a SiC gate turn-off thyristor (GTO) and SiC p-i-n diode operating at case temperatures up to 150°C. For high power and high voltage applications the GTO is the switch of choice. In this study, currents up to 2 A where switched by the GTO under pulsed and continuous switching into an inductive load. The turn-on and turn-off gains, the on-state voltage, and the turn-on and turn-off times, as a function of temperature will be discussed.

This paper reports on the first demonstration of a half-bridge power inverter constructed from silicon carbide gate turn-off thyristors (GTOs) operated in the conventional GTO mode. This circuit was characterized with input bus voltages of up to 600 VDC and 2 A (peak current density of 540 A/cm(2)) with resistive loads using a pulse-width modulated switching frequency of 2 kHz. We discuss the implications of the thyristor's electrical characteristics and the circuit topology on the overall operation of the half-bridge circuit. This work has determined the conservative critical rate of rise value of the off-state voltage to be 200 V/mus in these devices.

Future US Army motor control applications will require power devices to operate for thousands of hours at case temperatures of 150/spl deg/C and higher. For reliable operation of silicon (Si)-base power electronic, the operational case temperature must be below 120/spl deg/C. Because of this temperature limitation of Si, new wide bandgap materials such as silicon carbide (SiC) are being investigated. The wide bandgap material allows SiC devices to operate at temperatures significantly greater than 150/spl deg/C. For high power and high voltage applications the gate turn-off thyristor (GTO) is the switch of choice. This paper presents the results of a SiC GTO and a SiC p-i-n diode both operating at case temperatures up to 150/spl deg/C. The GTO switches into an inductive load with currents up to 5 Amps, baseplate temperature up to 150/spl deg/C and switching frequency up to 10 kHz.

SiC GTO thyristors may soon be the best available choice for very high-power switching. At this time, we have developed new operational techniques, growth requirements and pn-pn-pn type structures to address the issues of high on-state voltage, poor turn-off gain, and inability to reach predicted breakover voltages. We present these findings using experimental measurements and numerical simulations

Shubnikov-de Haas (SdH) oscillation and Hall measurement results were compared with HEMT de and rf characteristics for two different MOCVD grown AlGaN/GaN HEMT structures on semiinsulating 4H-SiC substrates. A HEMT with a 40-nm, highly doped AlGaN cap layer exhibited an electron mobility of 1500 cm(2)/V/s and a sheet concentration of 9 x 10(12) cm(-2) at 300 K (7900 cm(2)/V/s and 8 x 10(12) cm(-2) at 80 K), but showed a high threshold voltage and high de output conductance. A 27-nm AlGaN cap with a thinner, lightly doped donor layer yielded similar Hall values, but lower threshold voltage and output conductance and demonstrated a high CW power density of 6.9 W/mm at 10 GHz. The 2DEG of this improved structure had a sheet concentration of n(SdH) = 7.8 x 10(12) cm(-2) and a high quantum scattering lifetime of tau(q) = 1.5 x 10(-13) s at 4.2 K compared to n(SdH) = 8.24 x 10(12) cm(-2) and tau(q) = 1.72 x 10(-13) s for the thick AlGaN cap layer cm structure. Despite the excellent characteristics of the films, the SdH oscillations still indicate a slight parallel conduction and a weak localization of electrons. These results indicate that good channel quality and high sheet carrier density are not the only HEMT attributes required for good transistor performance.

Measurements indicate that in power conditioning circuits using SiC gate turn-off(GTO) thyristors, conduction losses can be reduced by injection of a portion of the load current through an electrode connected to the base regions so that it encounters only two back-to-back p-n junctions. Simulations of SiC GTO thyristors indicate that the maximum voltage blocked can be increased and the turn-off time reduced by an increase in the thickness of the p-type buffer layer (p+ base region). These simulations also show that it is permissible to have the drift region n-type whether the gates are on an n-base or ap-base. This option is desirable because high-quality thick n-type epilayers are easier to grow than p-type epilayers.