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Silicon carbide (SiC)-diodes have been commercially available since 2001 and various SiC-switches have been launched recently. Parallelly, gallium nitride (GaN) is moving into power electronics and the first low-voltage devices are already on the market. Currently, it seems that GaN-transistors are ideal for high frequency ICs up to 1kV (maybe 2kV) and maximum a few 10A. SiC transistors are better suited for discrete devices or modules blocking 1kV and above and virtually no limit in the current but in that range they will face strong competition from the silicon insulated gate bipolar transistors (IGBTs). SiC and GaN Schottky-diodes would offer a similar performance, hence here it becomes apparent that material cost and quality will finally decide the commercial success of wide bandgap devices. Bulk GaN is still prohibitively expensive, whereas GaN on silicon would offer an unrivalled cost advantage. Devices made from the latter could be even cheaper than silicon devices. However, packaging is already a limiting factor for silicon devices even more so in exploiting the advantage of wide bandgap materials with respect to switching speed and high temperature operation. After all, reliability is a must for any device no matter which material it is made of.

Silicon-based high-power devices continue to play an enabling role in modern high-power systems, especially in the fields of traction, industrial and grid applications. Today, approximately 30 years after its invention, a bipolar-metal-oxide semi-conductor controlled switch referred to as the insulated gate bipolar transistor (IGBT) is the device of choice for the majority of power electronics converters with power ratings ranging from few kWs to beyond the 1 GW mark. Following a brief introduction into power devices and applications in general, this paper will provide an overview of the development history and recent advancements of the IGBT. More importantly the future technology trends purely from the device design view point will be discussed including the predicted performance impact such technology platforms will have at the system level especially in the high-power range.

Analytical models have been proposed to describe the onset current density for the initial snapback in the transistor on-state mode and in the blocking state of reverse conducting-insulated gate bipolar transistors (RC-IGBT) for the stripe and cylindrical designs of the anode shorts. In cylindrical case, there are two possible ways in designing the anode shorts and the authors have proposed an analytical model for each of them. The considered RC-IGBTs are vertical with soft punch-through type buffer designs. The analytical model has been evaluated with the aid of 2-D device simulations and measurements. The authors have investigated the initial snapback phenomenon for different voltage class devices at a given technology (anode and buffer profiles) and found out that the snapback voltage increases with the blocking capability but not the snapback current density. The authors have also observed that the initial snapback phenomenon is more pronounced at lower temperatures. From the analytical model as well as simulation and measurement results, the authors have found that for a given voltage class and technology, the p+-anode width is the only remaining design degree of freedom which determines the initial snapback. The adjustment of the on-state losses can then be done with the proportion of the n+-short region.

The model of interconnected numerical device segments can give a prediction on the dynamic performance of large area full wafer devices such as the Gate Commutated Thyristors (GCTs) and can be used as an optimisation tool for designing GCTs. In this study the authors evaluate the relative importance of the shallow p-base thickness, its peak concentration, the depth of the p-base and the buffer peak concentration.

Power metal-oxide semiconductor field effect transistors (MOSFETs) are more and more used in atmospheric and space applications. Thus, it is essential to study the influence of the natural radiation environment on the electrical behaviour of vertical double-diffused metal-oxide semiconductor (VDMOS) and super-junction (SJ) MOSFETs. Two-dimensional numerical simulations are performed to define the sensitive volume and triggering criteria of single-event burnout (SEB) for VDMOS and SJ MOSFETs for different configurations of ionising tracks. The analysis of the results allows a better understanding of the SEB mechanism in each structure and allows the behaviour and robustness comparison for these two technologies under heavy-ion irradiation.

The reverse conducting-IGBT (RC-IGBT) is a well suited device for soft switching applications, that is, zero voltage switching (ZVS). However, standard RC-IGBTs are optimised for hard switching, which shows different switching waveforms compared with soft switching. In this study, the optimisation of the RC-IGBT is described for soft switching applications using the example of an induction cooker. The investigated induction cooker is implemented by using the single-ended quasi-resonant topology. Simulations show that main losses of the induction cooker occur in the induction coil and the RC-IGBT (power switch). The performance of the coil can be improved mainly by minimising the coil resistance. The IGBT-optimisation is based on the reduction of tail current in the soft switching mode. The IGBT thickness is decreased and the local lifetime is used to achieve lower tail current. A reduction of the overall losses by 30% is achievable. As a result, the cooling system of the IGBT can be smaller and cheaper.

The surge-current ruggedness of free-wheeling diodes can be improved by implementing the self-adjusting p emitter efficiency diode concept (SPEED). Simulations indicate that the switching ruggedness is reduced because of the occurrence of cathode-side filaments during reverse-recovery. Experiments confirm the weak switching performance of such a diode in comparison to a conventional diode. By implementing the controlled injection of backside holes concept cathode-side filaments can be suppressed. However, this measure is not sufficient to regain the switching ruggedness of a conventional diode. It is also necessary to fully embed the p+-areas of the SPEED anode in the low-doped p-type area to avoid high electrical field strengths at the p+p-junction and pinning of anode-side filaments. However, anode-side adjustments for improving the switching ruggedness can reduce the benefit of the SPEED concept regarding the surge-current capability.

An intelligent insulated gate bipolar transistor (IGBT) suitable to be used in remote-controlled on-load tap changers and traction applications is analysed in this study. An anode voltage sensor monolithically integrated in the active area of a 3.3 kV–50 A PT-IGBT is introduced to enhance the robustness of the IGBT against short-circuit events. The operation mode of the anode voltage sensor is described and TCAD simulations are performed to describe the static and dynamic performance together with the interaction between the sensor and the IGBT core cells. The study of the anode voltage performance under inductive turn-off conditions is also included, comparing the behaviour of IGBTs with and without anode voltage sensor.

Power device reliability is a multidisciplinary domain. It requires design and integration of sensors, implementation of signal processing algorithms that allow processing the different data provided by the different sensors in order to predict by statistical means the device failure occurrence and consequently anticipate the power device replacement. Currently, for device ageing studies in a laboratory, electrical measurements of device parameters are often used as an indicator of device ageing. Furthermore, smart metal-oxide semi-conductor technology integrates more and more sensors that permit to measure quantities such as on-state resistance or junction temperature of the device. In power vertical diffused metal oxide semiconductor (VDMOS) assemblies, it would be interesting to make use of the VDMOS electrical parameters deviations in order to monitor the ageing state of the power assembly. To that end, we carry-out in this paper a study mainly based upon electro-thermo-mechanical simulations in order to identify the power VDMOS electrical parameters that could be monitored in order to access to the mechanical state of the power assembly and therefore anticipate the assembly failure. The power VDMOS Ron as well as zero temperature coefficient (ZTC) point are of interest because they are sensitive to mechanical stress. Consequently, in this paper, a procedure to minimise temperature impact on the Ron of the VDMOS transistor such that one could use the Ron as mechanical state indicator is shown. Another solution that makes use of a specific operating point of VDMOS (ZTC) which is temperature independent is also studied by simulations and experiment.

This contribution investigates transient degradation of reverse characteristics of diodes by means of a noise measurement. This effect appears immediately after external heating or after a long time on-state polarisation of diodes (without a significant temperature growth of the device in this case). Simultaneously with the reverse characteristics degradation, the noise power measured under a low voltage DC reverse bias is influenced. The first possible cause of these effects is connected with so called slow surface states (SSS). The SSS are caused by the presence of material process induced defects in the region of a p-n junction surface termination. SSS have fundamental impact on the reverse properties of diodes and their low frequency noise behaviour. The second cause is connected with so called volume structural defects (VSD). Their origin can be ‘genetic’ (e.g. the presence of imperfection inside a silicon crystal) or they can be induced during technological processing. These defects are not repairable and under the reverse bias they will form so called ‘hot spots’ that is, places with a local high current density. Rapid and operative measurements of the noise power can reveal latent instabilities of reverse characteristics invisible during a standard inspection process during the production.