Comparison of the advantages of Qorvo SiC FET and SiC MOSFET

As shown in the figure, SiC has many technical advantages compared to silicon (Si) materials, so it is easy to understand why it has become a popular choice in many applications such as electric vehicles (EVs), data centers, and solar/renewable energy. Favored technology of choice.





Many end product manufacturers have chosen to use SiC technology to replace silicon-based processes to develop devices based on bipolar junction transistors (BJT), junction gate field effect transistors (JFET), metal oxide semiconductor field effect transistors (MOSFET) and insulated gate dual IGBT power supply products. However, the SiC "cascode structure" FET device developed by Qorvo (shown in Figure 2) takes this technology a step further. These devices are based on a unique "cascode" circuit configuration that co-packages a normally-on SiC JFET device with a silicon-based MOSFET to form an integrated normally-off SiC FET device. In the following paragraphs, we will elaborate on the significant advantages of the SiC FET (cascode structure FET) developed by Qorvo compared to similar SiC MOSFETs.



What advantages can be gained by using SiC compared to silicon-based devices?

SiC MOSFETs or SiC FETs have several significant advantages over silicon-based devices. First, SiC, as a wide band gap material, has a higher breakdown voltage, so thinner devices can be used to support higher voltages. In addition, SiC has the following advantages over silicon-based devices:



For a given voltage and resistance level, SiC can achieve higher operating frequencies, thus reducing the size of passive components and thus reducing the size and cost of the overall system.

For higher voltage levels (1200V or higher), SiC can achieve high-frequency switching with lower power losses; silicon-based devices that are still competent at such voltage levels are virtually non-existent.

In any given package, SiC has lower on-resistance and switching losses than silicon-based products

SiC enables customers to achieve higher efficiency, better thermal performance, and higher system power ratings in the same design as silicon devices

These advantages are also reflected in the performance of Qorvo SiC FETs. As a newer and more capable device, the Qorvo SiC FET is optimized for a variety of power applications and brings the following additional benefits:

The Qorvo SiC FET architecture uses standard silicon gate drivers, which smoothes the transition from silicon to SiC and provides designers with greater flexibility

Maximizes system efficiency with industry's lowest drain-to-source on-resistance RDS(ON) in a given package

Lower capacitance allows for faster switching speeds, resulting in higher operating frequencies; this further reduces the size of bulky passive components such as inductors and capacitors

Compared with silicon-based IGBTs, SiC FETs can achieve higher operating frequencies at higher voltage levels (1200V or higher). Silicon-based IGBTs, while traditionally serving this market segment, are generally slower and only used at lower frequencies and therefore have higher switching losses

Qorvo SiC FET devices enable smaller die size for a given RDS(ON) and alleviate gate oxide reliability issues common with SiC MOSFET products

SiC MOSFETs vs. Qorvo SiC FETs: An in-depth comparison

Let’s take some time to understand more deeply the differences between the two power technologies, SiC MOSFETs and Qorvo SiC FETs. From Figure 3 below, we will see that SiC MOSFET technology is different from Qorvo’s integrated SiC FET – and this is the result of careful design. Qorvo uses SiC JFET to eliminate the gate oxide layer of SiC MOSFET, thus eliminating the channel resistance and making the die size more compact.



The smaller die size of Qorvo SiC JFETs is a key differentiator and is best reflected by the ‘RDS(ON) x A’ (RdsA) figure of merit (FOM) shown in Figure 4. This means that for a given die size, Qorvo SiC FETs offer a lower on-resistance rating; in other words, under the same RDS(ON) conditions, Qorvo SiC FETs require a smaller SiC die size. Qorvo has established an industry leadership position with its outstanding performance in RdsA FOM; this is fully demonstrated by its ultra-low rated resistance products that can be used in relatively small industry standard packages such as TOLL and D2PAK.



Qorvo's SiC FETs have lower output capacitance Coss compared to SiC MOSFETs. Devices with lower output capacitance switch faster at low load currents and have shorter capacitor charging delays. This means that end equipment can achieve smaller size, lighter weight, lower cost, and achieve higher power density due to the reduced need for larger passive components such as inductors and capacitors.



SiC MOSFET also faces the following technical challenges:

SiC MOS has high channel resistance, resulting in low electron mobility

With higher gate bias, Vth can drift; this limits the gate-to-source voltage drive range

The body diode has a higher knee voltage and therefore requires synchronous rectification



However, after using Qorvo SiC FET, the above defects are fundamentally solved for the following reasons:

SiC JFET structure devices abandon the MOS (metal oxide) structure, so the device is more reliable

Lower drain to source resistance under the same chip area

Lower capacitance equates to faster switching transitions and higher frequencies

main conclusion

Although there are a wide variety of SiC power semiconductors available on the market, some devices do perform better than others in certain applications. Qorvo's integrated SiC "cascode" FET technology is one of the best; it provides excellent performance with its unique advantages of low RDS(ON), low output capacitance, and high reliability. These figures of merit enable Qorvo's SiC FET technology to shine in areas where other technologies cannot. In addition, the additional performance of SiC FETs enables higher efficiencies in AC/DC power units, DC/DC energy storage and renewable energy applications, and electric vehicle fast chargers.