Charge Sheet Super Junction in 4H-Silicon Carbide: Practicability, Modeling and Design

We discuss details of the Charge Sheet SuperJunction (CSSJ) in 4H-Silicon Carbide (SiC). This device was earlier proposed in Si material. A CSSJ is obtained by replacing the p-pillar of a SJ by a bilayer insulator, e.g., Al
₂
O
₃
/SiO
₂
; the inter-layer interface of this insulator has a negative charge-sheet, whose magnitude is easily controlled via the insulator deposition temperature. This charge-sheet depletes the n-pillar. Two potential advantages of this structural modification are brought out. First, it can avoid the problems related to SiC SJ’s p-pillar fabrication. Second, it can lower the specific-on resistance,
$R_{ONSP}$
, below that of SJ by 5–45 %, since SiC technology allows the insulator to be thinner than the p-pillar. The critical field,
$E_{C}$
, in SiC is > 10 times higher than that in Si. We give an analytical breakdown voltage,
$V_{BR}$
, model, which shows that the
$V_{BR}$
sensitivity to charge imbalance due to inevitable process variations is inversely proportional to
$E_{C}$
; hence, this sensitivity of CSSJ in SiC is > 10 times lower than that in Si. On the other hand, we give numerical simulations to establish that, in spite of
$E_{C}$
differences, the SiC CSSJ inherits the advantage of upto 15% higher
$V_{BR}$
compared to SiC SJ, from its Si counterparts. We show how our prior analytical procedure of designing a SJ can be adapted to design a CSSJ having a lower
$R_{ONSP}$
than the SJ, at a specified
$V_{BR}$
in 1–10 kV range and charge imbalance ≤ 20 %. Our work should strengthen the motivation for fabricating the CSSJ in SiC.