Application Specific Trade-offs for WBG SIC, GaN and High End SI Power Switch Technologies
Release Date:2022-11-21 17:20:36

In the face of technologies changing every day, SiC-FETs (MOSFET) and lateral GaN-HEMTs have remained to be one of the most important devices for power-switching technologies. With recent advancements in this field, SiC and GaN have played a huge role in increasing the performance of power devices and circuits comprising of high power applications. Furthermore, these devices have manifested in demonstrating higher efficiency with much-reduced production and implementation costs.

SiC-FETs (MOSFETs) and lateral GaN-HEMTs are two such components that have impactful achievements in the power semiconductor sector. When compared to traditional SiC wafers, GaN wafers can operate in similar environments with a significantly lesser rate of failures in terms of ruggedness and voltage derating. All powerrun between 600 and 1200 volts, therefore devices based on SiC and GaN, like JFETs, MOSFETs, and IGBTs, have extremely improved in this voltage range.


Ⅰ.  Competitive Situations in Power Switching Devices

 the on-resistance value between the drain and source (RDS,on) ideal for multiple MOSFETs, including ones like the Infineon CoolMOS family of MOSFETs. Modern SiC switch concepts promise a factor 5 lower on-resistance, but unfortunately, this is consumed by high SiC area costs for 650V devices. The ideal on-resistance value is 1Ωmm² and to achieve this value, the pitch of the cell is reduced by compensation accuracy. Observations during the experiment showed that energy stored in output capacitance or Eoss values of recently developed devices is reduced twice which makes it more similar to the values of SiC and GaN.



Utilizing local plasma density, the power densities of IGBTs rating from 650V-1700V are being improved and upgraded for increased effectiveness. In many cases, these devices are being inhibited by high resulting current and related low short circuit validity. This appears to be a limitation, but it can be addressed with proper diffusion soldering, sintering, and thicker front-side power metal acting as a temporary heat sink. Another disadvantage of the IGBT is missing an integrated free-wheelingwhich implies zero reverse conducting voltage. As a consequence of this, IGBTs are always preferable over all other power switch technologies. Unfortunately, with all current improvements, WBG switches are providing 1/10th of the switching losses if and only if the dV/it is high and the assembly setup is less inductive.


 Comparison of the energy stored in the output capacitance. Fig 2(b): Comparison of the charge stored in the output capacitance

Besides this, all IGBT losses being bipolar, such devices are T-dependent due to the continuous increase of minority carriers always. This leads to an increment in temperature issues by up to 40-50 per cent. Furthermore, a reverse conducting IGBT is considered an active gate control which decreases the minority carrier density before turning off the diode. Hence, this benefit depends upon the ratio between static and dynamic losses which may be dI/dt or dv/dt gradients.


GaN (Gallium Nitride) has a greater advantage than SiC but at the same time, is also a more difficult material to crystallize and process than SiC. HEMT technology forms elements only on the surface of a substrate on which GaN crystals are grown. GaN HEMTs differ from the others in a way that they have very low gates and zero recovery losses, and they exhibit destructive breakdowns rather than avalanches in others. These devices are based on n hetero-epitaxial material growth with low Rds to allow for high current densities, but they are hampered by low thermal capacitance. Switching losses occurring in GaN HEMTs are all independent of temperature as it is purely a capacitive loss similar to MOSFETs. GaN HEMTs lead to the risk of thermal runaway causing damage along with a possibility of short circuits. This is used up in drives, PFC after AC  drop out.


Ⅴ. Conclusion

The above table shows various devices with their voltage ranges and their respective attributes.

SiC-based IGBTs are considered the best-suited devices for high voltage ranges of 400V-6.5kV, whereas GaN-on-Si HEMTs are considered to be the best-suited devices for high voltage ranges of 400V-6.5kV.  Taking this into consideration, GaN-on-Si HEMTs are thought to be ideal for voltage ranges of 30V-600V. If cost as a criterion is kept aside, SiC devices have the upper hand in all aspects.  SiC-based devices have the benefit of operating through high voltage ranges without losing their blocking capacity.

It is made possible in the beginning by the accessibility of inexpensive GaN substrates in larger wafer diameters (150mm and 200mm). GaN would then make it possible to extend to higher voltage classes beyond 650V as a result by which, the boundaries of SJ and IGBT technology would also be reached. There are a number of ways to boost a device's productivity, but the challenge this faces is the feasibility of these methods, due to increased manufacturing costs. Overall, the price of devices is getting more competitive, and the importance of device application-specific uniqueness is rising. To improve efficiency and raise the reliability of power devices, more study and development must be done on various materials used in power semiconductor technology.


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