High Frequency Capacitive behavior of field stop trench gate IGBTs operating in Short Circuit
A wide experimental characterization about the input capacitance of Field Stop Trench Gate IGBTs is presented. It was achieved thanks to a novel experimental set-up which allows us to measure the input capacitance in the active region where the device operate during the Short Circuit (SC). The experimental results have been interpreted with the help of FEM simulations which confirm that negative capacitance is correlated with the accumulation of holes at the interface between N- IGBT base and gate oxide.
Investigation and Classification of Short-Circuit Failure Modes Based on Three-Dimensional Safe Operating Area for High-Power IGBT Modules
Insulated-gate bipolar transistor (IGBT) short-circuit failure modes have been under research for many years, successfully paving the way for device short-circuit ruggedness improvement. The aim of this paper is to classify and discuss recent contributions about IGBT short-circuit failure modes, in order to establish the current state of the art and trends in this area. First, the concept of 3-D safe operating area is proposed as the IGBT's operational boundary to divide the device short-circuit failure modes into short-circuit  $V_{{\rm{DC}}}/ V_{{\rm{rated}}}\hbox{--} I_{{\rm{SC}}}$ SOA limiting and short-circuit endurance time limiting groups. Then, the discussion is centered on currently reported IGBT short-circuit failure modes in terms of their relationships with the device 3-D short-circuit safe operating area (3D-SCSOA) characteristics. In addition, further investigation on the interaction of 3D-SCSOA characteristics is implemented to motivate advanced contributions in future dependence research of device short-circuit failure modes on temperature. Consequently, a comprehensive and thoughtful review of where the development of short-circuit failure mode research works of IGBT stands and is heading is provided.
Anomalous reactance behaviour during the impedance analysis of time-varying dielectric systems
Abstract Any real dielectric material deviates from ideal behaviour by exhibiting residual electrical conductivity, particularly at high fields and elevated temperatures. This conductivity is usually non-ohmic and often time-varying. During the a.c. impedance analysis of such a system, anomalous reactance behaviour may be observed including negative capacitance and low-frequency dispersion. We con-sider the characterization of dielectrics displaying time-varying conductivity and discuss their interpretation in terms of equivalent-circuit components. The situation is shown to be analogous to the Debye treatment of dielectric relaxation but with time-varying conductivity in place of time-varying permittivity. Quantitative relationships between the time-varying differential conductivity and the measured frequency-domain behaviour are derived and the origins of negative capacitance, low-frequency dispersion and related anomalous reactance effects are elucidated.