On The De-Rating of 4H-Silicon Carbide (SiC) Power Schottky Barrier Diodes

Abstract

Silicon Carbide (SiC) is the most promising material among all wide bandgap semiconductors for high-voltage and hightemperature power electronics. A careful analysis of the current state-of-the-art commercial 4H-SiC power Schottky Barrier Diodes (SBDs) indicates that these devices are operated well below their true avalanche breakdown potential. It is shown that the breakdown voltage ratings of commercial 4H-SiC power SBDs are lower than a factor of 2 compared to their true avalanche breakdown capability. A simple analysis is presented to determine the de-rating factor of 4H-SiC power SBDs using the information provided in the manufacturer's data sheets. The device de-ratings appear to be primarily due to a high-density of crystal defects in the drift-region of the device.

Current Status and Emerging Trends in Wide Bandgap (WBG) Semiconductor Power Switching Devices

“…20 Experimental results accumulated over the past two decades by researchers around the world clearly suggest that non-micropipe defects present in the bulk and epitaxial SiC material cause severe degradation in performance and reliability of SiC power devices. [21][22][23][24][25][26][27][28] More recently, it is becoming increasingly evident that SiC crystal defects also limit the voltage and current ratings of single-chip devices, [27][28][29] and hinder the development of cost-effective, energyefficient, and reliable SiC-based power electronics converters. Under high electric field strength and charge injection conditions, these other non-micropipe crystal defect sites lead to increased leakage currents, enhanced generation of local micro plasma, [21][22][23][24] and cause degradation in the forward current conduction characteristics of pin diodes.…”

“…25,26 To this day, these defects remain present in the commercial SiC bulk substrates and epitaxial layers to a density where their presence (and undesirable effects) must be accounted for in the manufacture of SiC commercial power devices. [27][28][29][30][31][32][33][34] Before the impact of such devices on circuit reliability was fully appreciated, early deployment of highvoltage SiC power Schottky barrier diodes (SBD's) in high-density, computer/telecom power supplies resulted in repeated field-returns. 9 Typical dv/dt failure characteristics are shown in Figure 11 for 600 V/6A 4H-SiC Schottky barrier diode (SBD) and 600 V/8A silicon merged pin and Schottky (MPS) barrier diode at a case temperature, T c = 25 • C. Whereas silicon MPS diodes did not fail even up to 100 volts/nano seconds, (limited to the testing capability of the measurement setup), SiC SBDs failed at a dv/dt of ∼55 volts/nano seconds.…”

On the Power-Handling Capability of Wide Bandgap (WBG) Semiconductor Power Switching Devices

“…After more than two decades of R&D efforts, the best single-chip SiC power devices commercially available are 1,700V/50A Junction Barrier Schottky (JBS) power diodes and 1,200V/60A power MOSFET's [2]. Unlike most silicon power diodes which are rated for avalanche breakdown, commercial SiC JBS power diodes have high leakage currents and are designed for punch-through, and hence, are not optimized for on-state conduction and switching performances [3]. Furthermore, important reliability parameters such as the dv/dt, avalanche and safe operating (SOA) ratings are not specified in the SiC power diode datasheets.…”