A High Transconductance β-SiC Buried-Gate Junction Field Effect Transistor

Abstract

An improved performance buried-gate junction field effect transistor (JFET) has been fabricated and evaluated. This structure employs an n-type R-SiC (111) thin film grown on the Si (0001) face of a p-type 6H β-SiC substrate. Electron-beam evaporated Ti/Au was used as an ohmic contact to the n-type β-SiC layer and thermally evaporated A1 was used to contact the n-type gate (substrate). Devices with 4μm gate lengths had a maximum room temperature transconductance of 20mS/mm, which is the highest reported for any β-SiC FET structure. The fabrication and performance of the improved devices will be compared with those of JFETs fabricated in similar β-SiC layers grown on a Si substrate. In addition, the experimental data have been analyzed using a charge control model. This analysis shows that the effective field-effect mobility (565 cm²/V-s) is close to the measured Hall mobility (470 cm²/V-s). Calculated drain current versus drain voltage (I_D-V_D) characteristics for a buried-gate JFET are in good agreement with the experimental data. Further improvements in device performance are anticipated as gate dimensions approach one micron or less.