Study of Different Edge Terminations Used for 6H-SiC Power Diodes

(Received 24 May 1996, revised 21 November 1996, accepted 19 December 1996)

Abstract
Silicon Carbide is a wide bandgap semiconductor (3 eV for 6H-SiC at 300 K) suitable for high voltage, high temperature, high frequency and power devices. Its drift velocity is high (  cm s ^-1), its thermal conductivity is similar to that of copper (5 W m C ^-1) and its critical electric field is almost 10 times higher than that of silicon. In the field of power devices, many publications refer to PN structures (4.5 kV), Schottky diodes (1.3 kV) as well as MOSFET and JFET. PN junction diodes have been designed and characterized with two different peripheral protections to achieve high breakdown voltage. The first protection is the MESA structure. In this approach, the curvature region of the main junction where the electric field is higher than in the bulk, is etched off. The efficiency of a P ⁺NN ⁺ MESA structure can be increased by decreasing the doping level of the N-type layer. For this purpose compensation by boron atoms is used for P ⁺NN ⁺ MESA structures. The second peripheral protection is a planar structure in which equipotential lines are spread around the lateral P-type low-doping implanted zones for P ⁺N junction or N-type Schottky diodes. The experimental breakdown voltage of these diodes lies between 600 and 1500 V.