Tranzistor de carbură de siliciu

Silicon carbide power devices play an integral part in improving energy efficiency of electric vehicles due to their excellent material properties.

Silicon carbide in its pure form behaves as an insulator; however, when doped with impurities (dopants), it can transform into an electronic semiconductor. Dopants for this use include nitrogen or phosphorous doping for n-type use while aluminum, boron or gallium doping can turn it into a p-type semiconductor material.

High Voltage Breakdown

Silicon carbide semiconductor devices are increasingly being considered a suitable replacement for silicon devices in power electronics applications involving high temperatures or voltages, particularly where high voltages or temperatures are involved. This is due to its exceptionally high breakdown electric field strength which means it can handle much greater current flows than silicon counterparts while withstanding up to 10x more voltage than MOSFETs – ideal for high voltage circuits used in electric vehicles and satellites.

CNTs stand out due to their larger bandgap, which is roughly three times greater than silicon’s 1.1eV, enabling electrons to more readily enter the conduction band for conducting electricity and making junction leakage currents less likely – key attributes in devices designed for reliable operation at higher temperatures.

Silicon carbide boasts a higher breakdown voltage due to its thinner depletion layer. This allows more free carriers through, increasing current density and permitting smaller transistors that require less energy; increasing efficiency and decreasing heat generation.

One of the major drawbacks to adopting silicon carbide technology has been its relatively high cost. But researchers have developed an inexpensive technique for producing silicon carbide power switches that make this material viable in high voltage applications.

They accomplished this through the application of a novel technique to combine unipolar and bipolar devices in one structure – known as merged pin-Schottky diodes or MPS diodes – which enabled them to compare characteristics between epitaxial and implanted junctions; epitaxial diodes proved more stable due to having higher reverse current resistance at high temperatures (RDS(ON)).

Silicon carbide could soon become more widely utilized for power electronics applications, benefitting both the economy and environment. Although SiC is already used in some applications such as LED light emitters and detectors for early radios, its vast potential means it could soon be found everywhere from terrestrial electric vehicles to instruments on rovers exploring Venus or probes designed to survive its extreme temperatures.

High Current Density

Silicon carbide is an extremely hard and dense material with several features that contribute to its success as an element in semiconductor devices. One such trait is its high breakdown electric field strength which allows devices made with it to tolerate much higher current densities than would otherwise be possible with silicon devices, making high power applications possible and faster switching times for larger loads. Furthermore, its lower ON resistance translates into reduced losses which is especially advantageous when designing power converters or similar designs.

Silicon carbide transistors feature high breakdown voltages that allow them to function at higher temperatures than other semiconductors, making them highly useful in high temperature applications such as power supplies for electric vehicles or equipment used on space missions. By helping reduce heat output in these devices, they can improve efficiency while increasing reliability.

Silicon carbide has long been recognized as a semiconductor material that can conduct electricity when doped with certain impurities, yet commercial quality devices made from this material were only recently realized due to its crystallinity forming into more than 150 polytypes, making growth suitable for electronic device fabrication more challenging than previously anticipated.

To create these new power semiconductors, a unique processing technique has been employed. This has been achieved using carbon ion beams followed by thermal oxidation or both processes in tandem to reduce carbon vacancy defect density.

SiC devices typically feature a unipolar transistor structure with a metal anode or p+n diode mounted to its top layer and an n-layer (voltage blocking region) connected to a low resistance substrate that allows current to flow when positive bias conditions exist, while blocking all current in negative bias conditions. This arrangement enables current to pass when positively biased but fully prevents it when negatively biased conditions exist.

Low On-Resistance

Silicon carbide (SiC) is well-known as an abrasive material and component used in bulletproof vest ceramics, but its semiconductor properties also make it a potential replacement for silicon-based devices in power electronics applications. SiC devices feature high blocking voltage capabilities, fast switching times and low on-resistance that help reduce losses when applied in applications like electric vehicle traction inverters and on-board chargers.

Silicon carbide’s electrical characteristics have long been recognized as superior to those of traditional silicon semiconductors. In particular, this wide bandgap material features an extremely high melting point, low dielectric constant and extremely high breakdown field strength – as well as having high saturated electron drift velocity and thermal conductivity values – all making it a standout candidate for use in electronic semiconductor device production.

However, until recently commercial quality devices constructed from silicon carbide remained an elusive goal due to its vast polytype diversity; creating large single crystals and thin films needed for MOSFET fabrication proved extremely challenging.

Cree and other companies were able to achieve breakthrough in silicon carbide technology with the introduction of Gate-Injection. This process allows devices to be driven with lower gate current, thereby decreasing temperature dependence of their on-state resistance while improving performance.

As such, MOSFETs can be safely driven to higher operating voltages without experiencing increased on-state resistance or parasitic effects such as gate oxide leakage – providing significant advantages over conventional IGBTs and bipolar transistors, which require derating when driven beyond their rated ratings.

UnitedSiC joined Qorvo’s family of companies in November 2021, providing low on-resistance silicon carbide FETs rated 750V/6mOhm that provide efficiency gains vital for high-power applications such as electric vehicle (EV) traction inverters, industrial power conversion and renewable energy systems. These FETs allow designers to reduce system size, weight and complexity while improving power density and reliability – key features critical to design.

Wide Bandgap

Silicon is one of the most widely-used semiconductors for electronic devices. But as its limitations in high power applications approach their limits, two compound semiconductor devices that offer solutions include gallium nitride (GaN) and silicon carbide (SiC) power transistors – each has unique benefits which make them excellent alternatives to standard IGBTs and Si MOSFETs in power conversion circuits.

Compound semiconductors feature wide bandgap properties, which enable them to operate at much higher temperatures than their silicon-based counterparts. “Wide” refers to an energy gap between their valence and conduction bands which is roughly three times wider than silicon’s 1.12eV gap allowing devices with this wider gap handle higher voltages and currents without thermal activation interference issues.

GaN and SiC can operate at higher switching frequencies, which in turn allows them to reduce power losses and increase efficiency in electronic circuits. GaN and SiC also boast voltage tolerance levels ten times greater than silicon, making them well suited to applications such as fast unipolar switches.

These semiconductors benefit from having larger bandgaps that enable thinner wafers than traditional silicon devices to be manufactured, leading to lower on-state resistance and an increase in critical breakdown field of their devices. Furthermore, this larger critical field enables devices of equal voltage rating with smaller devices to achieve a given voltage rating more cost efficiently and reduce size of power converters overall.

As demand for electric vehicles increases, so too does the need for reliable power electronics systems that can process and convert electrical energy into usable power. While silicon-based semiconductors have their limitations when used as power conversion circuit components, new developments have expanded what’s possible using wide bandgap semiconductors.

These new technologies are making power conversion systems significantly smaller and more efficient than ever before. Cree recently unveiled the industry’s first six-pack SiC MOSFET power module packaged in an industry standard 45 mm package, reducing power loss by as much as 75% while at the same time increasing power density by 50% and cutting total system cost by 70%.