High Temperature Electrical Characteristics of 20 A, 800 V Enhancement-Mode SiC VJFETs

摘要

The properties of silicon carbide and the absence of a critical semiconductor-dielectric interface make the SiC JFET a promising device for high temperature electronics. Recent papers have reported the temperature-dependent characteristics of depletion-mode SiC VJFETs; however, there have been few reports of enhancement-mode SiC VJFETs at high temperature. This paper describes the high temperature operation of a prototype 2.7mm~2 800 V enhancement-mode vertical-channel JFET originally designed for standard power supply applications. From 25 °C to 250 °C, the specific on-resistance (normalized to source electrode area) increased from 2.2 mΩ·cm~2 to 8.0 mΩ·cm~2 while the drain saturation current decreased from 21.5 A to 8.3 A. At 250 °C and V_(gs)= 0 V, the drain leakage current was 0.9 mA at 400 V and 5 mA at 600 V. The high temperature blocking performance of this device was limited by the reverse characteristics of the gate-drain junction and non-optimal threshold voltage. The threshold voltage varied linearly with temperature from +1.12 V at 25 °C to +0.70 V at 250 °C. Increasing the room temperature threshold voltage to +1.65 V improves the high temperature blocking performance as demonstrated with 0.86 mm~2 VJFETs. The total switching delay for the 2.7 mm~2 device was 158 ns which corresponds to a maximum switching frequency of 6.3 MHz.