1. Characteristics of SiC Schottky diodes

Schottky diodes have been around for a long time. This is a Schottky diode with a metal and semiconductor silicon contact

Schottky diodes are more like ideal switches than PN junction devices. The two most important properties of a Schottky diode are its low reverse recovery charge (qrr) and softening recovery factor.

When the diode voltage is reverse biased at a low qrr value, the reverse recovery time (TRR) is greatly reduced. The TRR of the Schottky diodes listed in the table below is less than 0.01. It is easy to use in the high frequency range, operating at frequencies up to 1 MHz (also reported up to 100 GHz). A high attenuation factor can reduce the EMI noise caused by diode disconnection and reduce the interference in switching operation.

Another advantage of silicon Schottky diodes over PN junction devices is low forward voltage and low conduction losses.

But Schottky diodes also have two drawbacks: firstly, the reverse voltage VR is low, only about 100V, and secondly, the reverse leakage current IR is large.

2. Characteristics of silicon carbide semiconductor materials and power devices

The band gap of SiC is 2.8 times greater than that of silicon, reaching 3.09 eV. Its insulation breakdown field strength is 5.3 times higher than that of silicon and reaches 3.2 mV/cm. Its thermal conductivity is 3.3 times greater than that of silicon and is 49 W/cm. K.

Like silicon semiconductor materials, it can be used to make junction devices, field devices, and Schottky diodes in contact with metals and semiconductors.

The benefits are:

(1) Silicon carbide single carrier device has a thin drift region and low on-resistance. This is 100-300 times smaller than silicon devices. Due to the low on-state resistance of SiC power devices, direct losses are low.

(2) SiC power devices have a high breakdown voltage due to the strong breakdown electric field. For example, the voltage of commercial Schottky diodes is less than 300 V, and the breakdown voltage of the first commercial SiC Schottky diodes reached 600 V.

(3) Silicon carbide has a high thermal conductivity, so the thermal resistance of the transition to the environment of silicon carbide power devices is low.

(4) Silicon carbide devices can operate at high temperatures. The operating temperature of silicon carbide devices is reported to be 600°C, while the maximum operating temperature of silicon devices is only 150°C

(5) Silicon carbide has high radiation resistance.

(6) The forward and reverse characteristics of SiC power devices do not change much with temperature and time, and they have good reliability.

(7) Silicon carbide deviceshave good reverse recovery characteristics, low reverse recovery current and low switching losses. SiC power devices can operate at high frequencies (> 20 kHz).

(8) Silicon carbide devices have made an important contribution to reducing the size and losses in the circuit of power devices.

3. Characteristics of SiC Schottky diodes!

As mentioned above, Schottky diodes have a low reverse withstand voltage of about 250V. Silicon carbide (SIC) is used to make devices capable of withstanding reverse voltages above 500-600V due to its ability to withstand higher voltages.

In addition, the parameters of the device are comparable or better than Schottky diodes. See Table 2 for details.

Due to the high cost of SiC devices (3-5 times higher than similar silicon devices), they have not been used to replace silicon power devices unless performance requirements are required.

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