Characterization of SiC PiN diode forward bias degradation

Abstract

An automated test system is developed and utilized to electrically monitor the emitter, base, and end region excess carrier lifetimes at periodic intervals during the forward bias stress of SiC PiN power diodes. The test system uses a specialized diode switching circuit, computer-controlled instrumentation, and model parameter extraction software. This lifetime measurement method is used to monitor diodes with degradation times ranging from one minute to over several hundred hours, and diodes that do not degrade. Diodes made from 11-20 crystal orientation material are also measured to examine the effects of stacking fault growth direction. Light emission studies are used to monitor the growth of stacking faults during the degradation. The results indicate that stacking fault growth and on-state voltage degradation are strongly correlated with a decrease in diode stored charge density and stored charge decay rate resulting from a reduction in effective end region lifetime and/or reduction in device conduction area. Degradation results from various crystal orientation devices indicate that a barrier to current traversing the plane of the stacking fault is primarily responsible for the change in electrical properties.

Experimental Evaluation of SiC PiN Diode Forward Bias Degradation and Long Term Stability

“…The current-time product is used to quantify the applied stress because V f degradation is generally observed to be a function of this product although there is often an independent current dependence as well. In many cases, the degradation rate exhibits some sporadic behavior due to initiation and termination of individual stacking fault propagations within the material [1].…”

“…Nonetheless, SiC minority carrier device types have been shown to be susceptible to degradation of the on-state voltage (V f ) when subjected to forward conduction stress. In general, the V f degradation is caused by SiC crystal stacking fault propagation, which has been studied in more detail in [1].…”

Advanced SiC Power Modules for 13.8 kV Power Distribution

“…Over the past few years, SiC power devices have begun to emerge with breakthrough static and dynamic performance compared with existing Si power diodes. Although rapid progress has been made toward commercialization of majority carrier SiC Schottky power diodes (Cree, Inc.; Infineon Technologies), a major challenge to the commercialization of high‐voltage conductivity‐modulated SiC power devices is the degradation of the on‐state voltage ( V f ) with forward bias stress (Hefner et al 2004). The full potential of SiC power devices to provide high‐voltage, high‐frequency (>10 kHz switching) power conversion cannot be met until long‐term reliability can be established.…”

“…Furthermore, it is widely known that as a SiC bipolar device is stressed, the Vf increases until it either stabilizes or continues until the device no longer conducts current. The amount of degradation is generally observed to be proportional to the current-time product and increases with increased temperature during stress (Hefner et al 2004). The SiC MOSFET operates in the unipolar mode; hence, Vf degradation is not observed during forward bias operation.…”

Computer-Controlled Characterization of High-Voltage, High-Frequency SiC Devices

“…1), 2) a 15 kV resistive and inductive load switching tester, 3) a 5 kV dI/dt and dV/dt controlled diode reverse recovery tester, 4) SiC model parameter extraction suite of tools, 5) a high-speed transient thermal current uniformity imaging system, 6) a highspeed transient thermal response system, 7) a rapid thermal cycling stress system, and 8) an automated multi-channel forward bias stress and monitoring system. Device degradation induced by forward bias stress is a reliability issue that is particularly important for minority-carrier type SiC power devices, such as PiN diodes and IGBTs [4]. The custom-made curve tracer program presented in this paper is a combination of hardware and software components capable of measuring I-V characteristics for HV-HF devices, for example, high voltage reverse leakage and gate leakage measurements for diodes and MOSFETs.…”