Silicon carbide thyristors for power applications

Silicon carbide has the potential to make high-performance power devices. Its high thermal conductivity, wide bandgap, high breakdown field and high saturated electron drift velocity imply a clear superiority over Si and GaAs. This work reports the fabrication and testing of three-terminal 6H-SiC thyristors. The silicon carbide thyristors show higher current density and higher temperature operation than is possible with silicon devices. Switching measurements at room temperature and at elevated temperatures are reported. SiC thyristors have demonstrated 650 V forward blocking voltage, 5200 A/cm/sup 2/ current density, 43 ns switching speed, and reliable 300 C operation. The device structures used in this work consist of a pnpn structure made from epitaxial layers grown on n-type 6H-SiC substrates. To improve electrical gating, the low-doped n-type gate region is N ion-implanted. Ohmic contact to the gate is then made using Ni metallization. Ohmic contacts to the p-type anode material and the n-type cathode material are made using Al and Ni (respectively). An electron cyclotron resonant plasma etching technique is used for gate recess and device isolation etching. Although these are small area devices, their performance demonstrates that power devices with high temperature capability can be made when material quality is sufficiently improved to allow fabrication of larger area devices. Mature devices are expected to find applications in military systems, utilities, and wherever compact thermal management systems or high temperature, high voltage, or high current operation is required.