Integrated Circuits and Materials

In MOSFET operation, the resistance between the Drain and Source when the device is fully turned ON is known as the ON Resistance, or RDS_on​. This parameter plays a critical role in determining the power loss during switching operations, particularly in power devices. A lower RDS_on ​ results in reduced conduction losses, which is essential for improving overall efficiency in power electronics systems. As RDS_on ​ decreases, less power is dissipated as heat, making it a key factor in optimizing performance, especially in high-current applications such as power supplies, inverters, and motor drivers. 

The plot in Figure 0497a illustrates the relationship between the on-resistance (RDS_on) of a MOSFET and the Gate-Source voltage (V_GS) at different drain currents (I_D). The on-resistance decreases with increasing Gate-Source voltage for all drain current levels, indicating that a higher V_GS leads to better conductivity in the MOSFET. Additionally, as the drain current increases, the on-resistance decreases more steeply for the same V_GS, suggesting that higher drain currents contribute to reducing RDS_on. This behavior is crucial for optimizing power efficiency in applications where MOSFETs are used to handle significant current loads, as minimizing RDS_on reduces conduction losses and heat generation.

Figure 0497b presents the specific ON-resistance of different SiC switches compared to modern silicon devices.

The device's performance of planar gate SiC MOSFET is limited by low channel mobility, primarily due to scattering at the 4H-SiC/insulator interface, which significantly reduces interface mobility compared to the bulk. Additionally, parasitic junction FET resistance contributes to higher conduction losses under forward operation. [16] A 4H-SiC planar MOSFET with a blocking voltage of 2.3 kV has been proposed, [17] featuring a gate oxide thickness of 27 nm, which provides an adequate gate oxide electric field. This device, fabricated using a commercial foundry, shows an improvement in specific on-resistance (R_on,sp) and a high-frequency figure of merit (FOM) by 1.3 times with a 15 V gate bias. Despite these benefits, the device experiences gate voltage overshoot failure due to the thin gate oxide. Another 4H-SiC planar MOSFET, designed with multiple floating guard-rings for edge termination, achieves a blocking voltage of 2.4 kV and a specific on-resistance of approximately 42 mΩ·cm². [18] This device demonstrates a channel mobility of 22 cm²/V·s and a threshold voltage of around 8.5 V.

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