A Surge Current Stable and Avalanche Rugged SiC Merged pn Schottky Diode Blocking 600V Especially Suited for PFC Applications

Abstract

Today silicon carbide (SiC) Schottky diodes are mainly used in the power factor control (PFC) unit of high end switched mode power supplies, due to their outstanding switching performance compared to Si pn diodes. In the case of the PFC it is required that the diodes are capable of handling surge currents up to several times the current of normal operation. The paper shows the surge current capability of a merged pn Schottky diode where the p-areas are optimized as efficient emitters. During normal operation the diode is behaving like a normal Schottky diode whereas during surge current condition the diode is behaving like a pn diode. For a sine half wave of 10 ms we achieved a non repetitive peak forward current capability of about 3700 A/cm2 which is about ten times rated current (for comparison: destructive current density of a standard Schottky diode ~ 1650 A/cm²). Additionally the device shows a stable avalanche and is able to withstand a single shot avalanche of 9.5 3s and 12.5 mJ.

Reliability aspects of SiC Schottky diodes

“…In the first case, 600 V Merged-PN-Schottky (MPS) diodes had been designed for improved avalanche ruggedness (see Refs. [10,11] and Fig. 5), in the latter case a deep n-implantation was introduced under the p + -part in the edge termination region (see Fig.…”

“…Thus, the electrical field E at the Schottky interface is significantly reduced and everywhere in the edge termination it is lower than E max . By that means, avalanche breakdown occurs well distributed in the cell structure, giving homogenous power dissipation in the whole active area of the device [10,11].…”

“…Infineon's MPS diodes are able to withstand pulsed repetitive avalanche with very high average power density in the range of 30 W/mm 2 [10,11]. In this study an HTRB-like test setup was used which allows a continuous reverse biasing under controlled avalanche current conditions (2-3 mA).…”

“…a). Details of the device structure and fabrication are given in[10], they are available as Infineon's 2nd Genera-www.pss-a.com © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Feature Article max. E field at p corners max.…”

Some Critical Materials and Processing Issues in SiC Power Devices

“…SiC MPS diodes have been used for their surge capability by utilizing the injection from the internal p-n diode at >3 V forward bias. 18 This is not recommended in high-voltage devices to prevent the formation of SFs. The high-voltage SiC MPS diodes should be bypassed by a silicon p-n diode for surge capability.…”