A V-groove Schottky-barrier FET for UHF applications

The structure and fabrication of a Schottky-barrier gate FET (SB-VFET) with a nonplanar conduction channel fabricated by preferential etching of silicon axe described in this paper. The device exhibits high transconductance and low series resistance and is suitable for low-noise applications at the lower end of the microwave spectrum. The low-frequency transconductance per unit channel length of 6 µm-gate device was typically 18.8 mΩ/mm, the gate breakdown voltage was 7 V, and the cutoff frequency was 1.3 GHz. The noise figure with the device biased for maximum gain was typically 4 dB at 350 MHz. A simplified theory adequate for engineering design purposes is proposed to explain the characteristics of the device and an equivalent circuit is used to model the high-frequency behavior. The theory is shown to be in agreement with experimental results. Frequency limitations of the present device are discussed and further improvements are proposed.