Review of high voltage silicon carbide device research at the army research laboratory

Summary form only given. The U.S. Army Research Laboratory has conducted research on high voltage silicon carbide thyristors and diodes in support of the Army´s pulsed power applications. Such applications require light-weight, power-dense components to enable mobile platforms. The Army Research Laboratory is seeking to optimize thyristor and diode capability at the single device level, then integrate chips into larger modules to meet high voltage and high current switching needs. Compared to silicon semiconductors, silicon carbide´s high breakdown field enables thinner high-voltage devices. The narrower drift region in turn facilitates faster turn-on capability and lower switching losses at very high voltages and current densities. The material´s thermal conductivity and high Young´s modulus make it ideal for high-power pulsed switching applications. Recent research developments that have increased die size, yield, and voltage blocking include production of larger material wafers, reduction in micropipe density, and reduction of basal plane dislocations. Progress in material growth and device design has led to development of 9 kV, 1.0 cm² silicon carbide Super-GTOs and P-i-N diodes. The devices evolved over the past five years through cooperative agreements which leverage Silicon Power Corporation´s design and packaging techniques with Cree, Inc.´s material growth and fabrication capabilities. The program started with 3 kV, 0.16 cm² Super-GTOs and 6 kV, 0.5 cm² diodes in 2006. Each device iteration was evaluated under pulse stress conditions at the Army Research Laboratory. Important parameters recorded were DC voltage blocking, peak pulse current density, dl/dt, on-state voltage drop, recovery time, and stability. The performance of each design was compared back to earlier generations, as well as to similar silicon switches, in order to verify progress and determine the path forward. Most recently, the 1.0 cm² Sup- r GTO was switched at a 120-μs wide pulse current as high as 5 kA (6.8 kA/cm² over the active area), with a dl/dt of 400 A/μs. P-i-N diodes were packaged in pairs and switched in series with asymmetric GTOs to provide reverse voltage protection. Presently, GTOs are being packaged into 16-chip modules expected to switch >;60 kA. This paper will go into further detail of the design iterations, device and module performance, and future work.