DocID024196 Rev 1

13/26

AN4242

New 650 V JBS SiC diodes

3

New 650 V JBS SiC diodes

3.1

Device structure

Figure 9. Comparison between a pure SiC Schottky structure with the

JBS SiC structure

The 2nd generation SiC device is based on JBS (junction barrier Schottky) concept. At high

forward voltage drops, this structure benefits from the injection of minority carriers by the PN

junctions inserted within the main Schottky contact. Thus in case of surges current,

increased compared to standard Schottky diode.

3.2

Comparison between first and second generation of SiC

diodes

3.2.1

Forward voltage comparison

The forward voltage characteristics of the first and the second generation are compared in

Figure 10. The dotted line network corresponds to the linear characteristics of the pure SiC

Schottky diode. The positive thermal coefficient is evident. Those curves highlight the

difficulties in characterizing the pure SiC Schottky diode at high current with constant

junction temperature due to the overheating linked to the measurement. To limit this thermal

SiC diodes also presents a linear characteristic up to a certain level of current. A clamping

effect linked to the JBS structure then appears at higher current. This effect happens when

Schottky barrier

Guard ring

4H - SiC epitaxy

N-type 4H - SiC epitaxy

4H - SiC substrate

N+ 4H - SiC substrate

Schematic cross section of conventional SiC Schottky diode (1st generation device)

Schematic cross section of a JBS SiC diode (2nd generation device)

Ohmic contact

on P+

Passivation

Top metal

Ohmic backside contact

Schottky barrier

P+

P+

Schottky

on N-type

Schottky

on P-type

PN junction

Metal

Schottky

area

N - epitaxy

N+ substrate

P area