0018-9499 (c) 2018 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TNS.2019.2914494, IEEE Transactions on Nuclear Science Abstract—The thermal runaway in SiC Schottky barrier diodes caused by heavy ions was identified by a device simulator with parameters carefully extrapolated to an extended temperature range far exceeding the melting point of SiC. It is shown that the critical electric field needed to activate the impact ionization attributable to SiC material and the Schottky barrier contact on it are responsible for thermal runaway in SiC SBDs Index Terms—Single-event burnout, SiC Schottky barrier diode, Thermal runaway, Radiation damage I. INTRODUCTION IC power devices are now being widely adopted in power electronics systems such as electric vehicles (EVs) and are also planned to be used in aerospace applications, given the expected reductions in weight, size, and power loss. However, the susceptibility of SiC Schottky barrier diodes (SBDs) to heavy ions is recognized as a critical issue for space applications [1]-[5]. The response to heavy ion irradiation is quite different from that observed in Si diodes. SiC SBDs are intended to replace Si p-n junction diodes (JDs) with a rated voltage of 600 V and higher, because the Si SBD technology that achieves lower power loss than Si JDs is only applicable up to 200 V of the rated voltage for commercial products. Therefore, the response of SiC SBDs to heavy ions is generally compared with Si JDs having the same rated voltage. Most Si JDs are immune to heavy ions with LET of around 60 MeV/(mg/cm 2 ) up to their rated voltage. In contrast, SiC SBDs begin to exhibit unexpected behavior at very low applied voltage. The first unexpected behavior is enhanced charge collection [2], where Manuscript received September 16, 2018; revised manuscript received February 21, 2019; accepted April 24, 2019. Satoshi Kuboyama is with Japan Aerospace Exploration Agency, Tsukuba, Japan (e-mail: kuboyama.satosho@jaxa.jp). Eiichi Mizuta is with Japan Aerospace Exploration Agency, Tsukuba, Japan (e-mail: mizuta.eiichi@jaxa.jp). Yuki Nakada is with Japan Aerospace Exploration Agency, Tsukuba, Japan (e-mail: nakada.yuki@jaxa.jp). Hiroyuki Shindou is with Japan Aerospace Exploration Agency, Tsukuba, Japan (e-mail: shindou.hiroyuki@jaxa.jp). Alain Michez is with Université de Montpellier, Montpellier, France (e-mail: alain.michez@umontpellier.fr). Jérôme Boch is with Université de Montpellier, Montpellier, France (e-mail: jerome.boch@ies.univ-montp2.fr). Frédéric Saigné is with Université de Montpellier, Montpellier, France (e-mail: frederic.saigne@univ-montp2.fr). Antoine Touboul is with Université de Montpellier, Montpellier, France (e-mail: antoine.touboul@ies.univ-montp2.fr). the collected charge is larger than the charge deposited by each heavy ion. In the region of increased applied voltage, an increase in permanent leakage current is observed as a linear function of ion fluence [1]-[5]. At a higher applied voltage but less than the rated one, catastrophic failure known as single-event burnout (SEB) is observed for all the commercially available SiC SBDs submitted for evaluation using heavy ions with LET of around 60 MeV/(mg/cm 2 ) [1],[2],[5]. It was recently suggested that the damage was induced by high temperatures exceeding the melting point of SiC (≈3100 K) at the Schottky contact resulting from enhanced current flow along the ion track attributable to impact ionization [4],[5]. It was surprising that the events were observed at less than 50% of their rated voltage. In general, an ion strike in the reverse biased diode structure generates strong electric field regions locally at boundaries in the structure such as the epi-substrate interface. Minority carriers (holes for n-type epi-substrate interface) generated in the epi-layer leave the interface, resulting in holes no longer being supplied from the substrate due to the lack of available holes there, whereas electrons generated in the epi-layer move towards the interface with the density being temporarily sustained by electrons generated in the ion track. However, a strong field region is not sustained where the mechanism of impact ionization takes place as the electron-hole pairs generated by impact ionization increase the electrical conductivity and neutralize the electric field. This is true regarding generic Si JDs, for which no SEB testing is required. There should be a specific mechanism attributable to the structure or material in SiC SBDs. An understanding of such mechanism is thus important to improve the susceptibility of SiC SBDs to heavy ions. In this study, a comparative analysis with Si JDs was conducted by using device simulations. As a preparatory stage, the behavior of the electrical parameter models for SiC material in the extrapolated temperature range is carefully investigated to avoid generating nonphysical values, such as a negative bandgap during device simulations. Finally, a thermal runaway process was identified as a mechanism responsible for the susceptibility of SiC SBDs to heavy ions. II. DEVICE SIMULATIONS A. Device Simulator The device simulator used in this study is ECORCE [6]. It uses a drift-diffusion model coupled with the heat equation (i.e., thermodynamic simulation with lattice temperature) and Thermal Runaway in SiC Schottky Barrier Diodes Caused by Heavy Ions Satoshi Kuboyama, Eiichi Muzuta, Yuki Nakada, Hiroyuki Shindou, Alain Michez, Jérôme Boch, Frédéric Saigné, and Antoine Touboul S