Characterization of 6H-SiC JFETs for use in a temperature monitor operating from 25°C to 350°C

6H-SiC buried-gate n-channel depletion-mode Junction Field-Effect Transistors (JFETs) manufactured by Cree Research, Inc. were characterized from 25 to 350°C in terms of transconductance (g_m ), pinchoff voltage (V_p), output resistance (r₀ ), input resistance (R_in), drain-to-source current at zero gate-to-source voltage (I_DSS), gate-to-source reverse biased leakage current (I_GSS), off-state drain-to-source current (I_DSS(off)), and noise power spectral density (S_V ). Degradation of the small-signal voltage gain (to ~1 at 350°C) as a result of increasing output resistance, was found to be the most serious device shortcoming. The 6H-SiC JFETs were tested for use in a temperature monitoring circuit (from 25 to 350°C) currently under development at Auburn University for use in automotive and other industrial applications. A SPICE model was developed to match the experimental data obtained from the 6H-SiC JFETs and diode. The SPICE simulation of the temperature monitoring circuit's output voltage corresponded well with measured data as a function of temperature. Maximum temperature percent error was 2.4% over the temperature range of 25 to 350°C