Super Gate Turn-off Thyristors Research Articles

Safe Operating Area and Long-Term Reliability of 9-kV Silicon Carbide PNPN Super Gate Turn-Off Thyristors

One of the major requirements for adoption of new silicon carbide (SiC) super gate turn-off thyristors (SGTOs) into high-energy applications is to verify the safe operating area and long-term reliability capabilities of these devices. In this letter, we have developed a unique high-energy testing system that can evaluate the performance limitations with respect to lifetime capabilities of the 9 kV, 1 cm 2 , SGTOs at ultrahigh pulsed current levels from 1 to 3.5 kA. The test system produces square current pulses with a user specified current amplitude and a 100-μs pulsewidth at a maximum repetition rate of 1 shot/s (>0.1% duty cycle). A lifetime safe operating area with respect to maximum pulsed current was then established that these 1 cm 2 , 9 kV, SiC SGTOs can perform reliably without significant degradation at pulsed current levels up to 2.0 kA. At current levels above 2.0 kA shifts in the on-state voltage are observed probably due to device over-heating at such high current levels and having not enough time to fully dissipate the heat between any two shots, which results in the device rapidly deteriorating due to increased on-state losses ultimately leading to premature failure.

PULSE EVALUATION AND RELIABILITY ANALYSIS OF 4H-SiC SGTO MODULES

Army applications require power components that are utilized in pulsed power systems to be reliable and durable, compact, have high power and energy density, and lastly, to be easily integrated into combat vehicles. The U.S. Army Research Laboratory (ARL) is currently investigating silicon carbide Super-gate turn-off thyristors ( SiC SGTOs) to meet the future pulsed power system requirements for the Army. ARL's methodology is to evaluate the device performance in pulsed power circuits that emulate the electrical stresses that the power devices would encounter in a pulsed power system. Each module being evaluated utilized four 0.6 cm2 SiC SGTOs. The packaging design for the module utilizes ThinPak technology. The module has reliably been pulsed over 2000 times at peak currents greater than 8 kA with a pulse width of 170 μs. The module has also been pulsed greater than 3.6 kA at a pulse width of 1 ms, corresponding to an action rate of 7000 A2s and a current density of 2.5 kA/cm2 over the cathode mesa area. This work evaluates SiC SGTO modules under various pulsed conditions. This paper includes details on device structure, module package design, and module pulsed switching and reliability.

The benefits and current progress of SiC SGTOs for pulsed power applications

Silicon Carbide (SiC) is an extremely attractive material for semiconductor power devices because of its electrical and physical characteristics. This paper describes the benefits of utilizing SiC Super Gate Turn-Off thyristors (SGTO) in pulsed power applications, reviews the current progress and development of SiC GTOs, and presents the static and pulsed characteristics of large area GTOs with high blocking capabilities. The wide pulsed evaluation of the 0.5 cm 2 SiC SGTOs has been demonstrated and reported by the Army Research Laboratory (ARL). This paper presents the wide pulsed capabilities of the 1 cm 2 SiC SGTOs. The 1 cm 2 SiC SGTO devices handled up to twice the peak current of the 0.5 cm 2 SiC SGTOs at a 1 ms pulse width. The wide pulsed evaluation of these devices was demonstrated at ARL. ARL evaluated the static and pulsed characteristics of six of these devices. The devices had a forward blocking voltage rating of 9 kV and a trigger requirement of a negative pulse of 1 A to the gate for a millisecond pulse width. These devices were pulsed as high as 3.5 kA at 1 ms, equating to an action rate of 6 × 10 3 A 2 s and a current density of 4.8 kA/cm 2, based on the device active area. The narrow pulsed evaluation of this device has been demonstrated by Cree Inc. A peak current of 12.8 kA with a pulse width of 17 μs (corresponding to 12.8 kA/cm 2 based on the chip size) was conducted with this device.

Evaluation of Si and SiC SGTOs for High-Action Army Applications

The U. S. Army Research Laboratory (ARL) has been exploring silicon and silicon carbide Super gate turn-off thyristors (SGTOs) for high power pulse switching required by Army survivability and lethality applications. Silicon SGTOs (3.5 cm2) were pulsed at 5 kA with a half-sine current waveform measuring 1 ms at the base. The recovery time, or Tq, of the devices was evaluated from the point at which the main current pulse fell to zero. Using a driver designed to provide both turn-on and turn-off signals, the Tq was reduced to 10 mus. Smaller silicon carbide SGTOs (0.16 cm2) were similarly evaluated for wide-pulse performance. They were switched several times at a peak current above 300 A, with an unassisted Tq time of 30 mus. This paper provides details of the aforementioned pulse switching, as well as a description of continuing evaluations involving parallel devices and larger test beds.

Evaluation of Advanced Si and SiC Switching Components for Army Pulsed Power Applications

Super gate turn-off thyristors (SGTOs) implemented in both silicon (Si) and silicon carbide (SiC) semiconductors were investigated for high-voltage, high-current pulsed power applications. Modular 80 and 400 kA switches implemented in silicon (2.0-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> dies) and individual SiC switch die (0.16 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) were evaluated. The Si 80- and 400-kA switches were demonstrated (at ambient temperature) to provide rates of current rise (10%-90% peak current) and peak currents (145-mus width) of 24 kA/mus and 92 kA; and 40 kA/mus and 400 kA, respectively. The Si 80-kA switch was repetitively pulsed 1000 times with no significant performance degradation. The SiC switch die were demonstrated to provide specific rate of current rise and current density of 49 kA/mus/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 56.1 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which are at least 2.5 times greater than are possible in silicon pulse switches. The SiC switches were repetitively pulsed at 5 Hz up to 99 000 times without failure and were demonstrated to operate at case temperatures up to 150 degC