Circular and linear enhancement-mode 6H-SiC MOSFETs for high temperature applications

Direct current measuremements are performed up to 673K at circular and line ar (shown in parenthesis) enhancement mode metal oxide semiconductor field effect transistors (MOSFETs). These devices are fabricated on a p-type 6H-S iC epitaxial layer with a doping concentration N-A approximate to 1 x 10(16 ) cm(-1). The n(+) source/drain regions and the p(+) regions for the channe l stops are achieved by ion implantation of nitrogen and aluminum, respecti vely. Both MOSFET geometries show excellent output characteristics with a g ood saturation behavior even at elevated temperatures. The inversion layer mobility mu(n) extracted in the linear region is 38 cm(2).V-1.s(-1) (35 cm( 2).V-1.s(-1)) and reveals a weak dependence on temperature with a maximum o f 46 cm(2).V-1.s(-1) (42 cm(2).V-1.s(-1)) at about 473K. Regarding the tran sfer characteristics, the drain current I-D can be well modulated by the ga te-source voltage V-GS resulting in an I-on/L-off-ratio of 10(8) (10(8)) at 303K and 10(5) (10(6)) at 673K. In the subthreshold regime, I-D can be pin ched off well below 10 pA with a subthreshold swing of 150 mV/decade (155 m V/decade) at room temperature. The threshold voltage V-T as a function of t emperature shows two linear sections with negative temperature coefficients of -6.8 mV.K-1 (-6.8 mV.K-1) from 303 to 423K and -2.5 mV.K-1 (-2.0 mV.K-1 ) from 423 to 673K. By measuring V-T as a function of bulk-source voltage V -BS at different temperatures, N-A can be directly estimated at a transisto r and gives 9.6 x 10(15) cm(-3) (9.8 x 10(15) cm(-3)). The measured bulk Fe rmi potential Phi(f) of the p-type epitaxial layer deviates less than 10% f rom the calculated value ata given temperature.