Search

The dependences of the common-emitter current gain [beta.sub.CE] on the collector current [I.sub.C] are measured at elevated temperatures for 1-kV 30-A 4H-SiC epitaxial emitter n-p-n bipolar junction transistors (BJTs). The minority carrier lifetimes and surface recombination velocity are obtained by the means of the simulation of a model that takes into account the main processes affecting the current gain.

Research involving design of SiC-based p-IGBTs is described and discussed.

A planar 4H-SiC accumulation channel field effect transistor (ACCUFET) is designed, fabricated and characterized. A detailed two-dimensional (2-D) simulation design suggests that the optimum spacing between two-adjacent p+ regions is approximately 4 mu m.

The design, fabrication and high temperature characteristics of 4H-SiC p-i-n rectifiers are described. The results were achieved from two lots in order to increase the total power levels on the rectifiers.

The 4H-SiC JBS diode offers nearly zero reverse-recovery charge. The use of the SiC JBS diode in hard switching applications eliminates the reverse recovery and the associated transistor turn-on current, as indicated by the experimental results.

The capabilities of high power SiC Schottky and PiN diodes are presented and their applicability to a large variety of ultrafast circuits and pulsed power applications is shown. The design guidelines and practical issues for the realization of high-power Sic Schottky and PiN diodes are presented.

Silicon Carbide (SiC) MOSFETs have achieved high blocking voltages and performance figures-of-merit. However, they are still not economically competitive with the silicon devices, as there are two aspects of SiC MOSFET that require further improvement.

A general estimation can be made of the carrier lifetime in the base, in high-voltage SiC diodes, using steady-state current-voltage characteristics at high injection levels. The transient time of the switch-on process can also be used for an estimate. Given an estimate of lifetime magnitude, the injection efficiency of the emitter can be evaluated.

The authors compare experimental and theoretical results of tests measuring transient current in diodes and thyristors. Topics include thermal conductivity, electron drift, and current density.

Significant improvements in high-temperature reliability of SiC metal-insulator-semiconductor devices have been achieved using both thermally grown oxides and a stacked dielectric containing silicon oxide-nitride-oxide. To demonstrate this observation, capacitors of p-type 6H-SiC, n-type 6H-SiC and n-type 4H-SiC were fabricated with different insulators. Insulators that incorporate silicon dioxide turned in the best performance. In addition, a new thermal oxidation process of growing a dry oxide followed by a wet re-oxidation anneal yields an oxide with the dielectric strength of a dry oxide and the high-quality interface of a wet oxide.

Research shows that the critical charge density of 4H-SiC thyristors is two times ten (super 15) centimeters (super -3) and ten (super 14) centimeters (super -3) at a forward voltage of five and 100 volts and 560 degrees kelvin. Experiments using maximum voltage ramp determine anode current density levels of between three and 7.5 times ten (super 2) angstroms per centimeter squared.

Silicon carbide has great potential for use in power semiconductor devices because of its high electric breakdown field, high saturated electron drift velocity and high thermal conductivity. 4H-SiC Schottky barrier diodes with forward current densities over 700 A/sq.cm. at 2 V are shown. Packaged SIT's have produced 57 W of output power at 500 MHz. SiC UMOSFET's are expected to have 15 times the current density of Si IGBT's.